I found this article but looks more jailbreak pro then con, so read carefully and be judgemental.

I feel he side steps many issues with no thats no problem it will work sometimes bla, bla.

The good point about this article it provides the Apple issues of Jailbreaking,,, we seem some lately like no GPS, overheating battery.. etc...

==Begin===
Apple has long been opposed to jailbreaking, even going as far as to try and declare jailbreaking illegal. If you jailbreak your iPhone or iPod touch your warranty is void (although often times they have no way of telling) as well, and that alone puts many people off. However, jailbreakers do make up a solid percentage of iDevice users (by most accounts roughly 10%), and with simple, quick and easily available jailbreak tools such as redsn0w it has never been easier to jailbreak.
However, lately Apple has been trying to scare people with a list of why you shouldn’t jailbreak. While it does present some reasonable arguments, a great deal of the article (found here if you would like to read it in it’s entirety) consists of dubious (at best) reasons. So I thought I might go through it and give my own opinions on it.

Device and application instability: Frequent and unexpected crashes of the device, crashes and freezes of built-in apps and third-party apps, and loss of data.
So the first reason is that jailbroken apps can crash your phone, resulting in loss of data. This is perfectly true; anyone who has been jailbroken for any length of time knows that crashes become somewhat more common, especially when you install more and more add-ons and jailbroken apps. Not to mention the fact that, when you update your iDevice to jailbreak it more often than not you will need to reset it and lose your data anyway.
That said, the idea that merely jailbreaking your device will instantly make it a glitchy mess is ridiculous. Simply jailbreaking doesn’t really change anything, it’s the apps that you download that can cause problems. However, in general the majority of jailbroken applications are quite well built and will rarely cause you problems. In the case that something is causing problems, merely uninstalling it will fix the issue.
Besides, Apple makes it out like the core OS is perfectly bug and lag free, which is obviously not the case at all. Even if you don’t jailbreak, you’re going to have to deal with lag and crashes at least sometimes.

Unreliable voice and data: Dropped calls, slow or unreliable data connections, and delayed or inaccurate location data.
This is totally false. Jailbreaking makes no real difference to the cellular capabilities, unless you unlock it for another carrier or circumvent the rules that don’t allow apps such as SlingPlayer and Skype to work over 3G or EDGE. Assuming you aren’t actually hacking around yourself deep in the phone, there is almost no fear of disrupting your cellular capabilities.

Disruption of services: Services such as Visual Voicemail, YouTube, Weather, and Stocks have been disrupted or no longer work on the device. Additionally, third-party apps that use the Apple Push Notification Service have had difficulty receiving notifications or received notifications that were intended for a different hacked device. Other push-based services such as MobileMe and Exchange have experienced problems synchronizing data with their respective servers.
This is partially true: there have been issues about push notifications on jailbroken phones (namely the notifications going to other devices sometimes). Visual Voicemail has sometimes been disrupted with certain hacks such as the modification that allows you to tether, however basic jailbreaking usually leaves your Visual Voicemail perfectly functionable. As for problems with YouTube, Weather and Stocks, I’ve personally never heard of any problems with any of these apps. To be honest, I’m not really sure how they could be negatively effected unless you started running a bad add-on for them or something.

Compromised security: Security compromises have been introduced by these modifications that could allow hackers to steal personal information, damage the device, attack the wireless network, or introduce malware or viruses.
This is true, a jailbroken iDevice is absolutely simple to break (assuming that a hacker physically has the device). However, security on all iPod touches and iPhones is pathetically weak anyway. Anyone with any kind of moderate tech knowledge could extract all the data off your device in minutes without even leaving a trace. Jailbreaking it and then extracting the data that way would be even easier.
As for viruses, technically this could be true. However there hardly is any malware or viruses in circulation right now (the possible exception being the hyped text message exploit which any iPhone, jailbroken or not, was vulnerable to) for the iPhone and iPod touch. That’s not to say that there might not be in the future, but right now it really isn’t a problem.

Shortened battery life: The hacked software has caused an accelerated battery drain that shortens the operation of an iPhone or iPod touch on a single battery charge.
This is probably the truest thing on the list. One of the bigger downsides against jailbreaking is the fact that your battery life can easily be negatively effected. However, as with most any of the problems that are listed here there are simple fixes: limit the amount of jailbroken apps you install. Between WinterBoard and Backgrounder your battery will certainly take a beating, but the beauty of jailbreaking is that if something is causing you problems, whether it is reduced battery life, extra memory useage or crashes, there is always a simple fix: uninstall it.
Using jailbroken apps in moderation, however, you will find that a jailbroken iDevice will likely get very similar battery life.

Inability to apply future software updates: Some unauthorized modifications have caused damage to the iPhone OS that is not repairable. This can result in the hacked iPhone or iPod touch becoming permanently inoperable when a future Apple-supplied iPhone OS update is installed.
This is technically true, however there is a very simple fix: don’t update your device. When you jailbreak, if you update you will lose your jailbreak and there is a chance that Apple could brick your device with an update. The best thing to do is to wait for the update to be tested out, usually by the iPhone Dev-Team. However, so far there have been no real problems with updating, whether you want to keep jailbroken or just restore the device to it’s factory setting.
If you are thinking about jailbreaking, I recommend that you think about why you want to. There is an element of risk involved (although the vast majority of the time the worst that can happen is that you will need to just restore), and there are potential drawbacks in the form of battery life and stability. For most people, it’s worth it. Whether it’s the customization, the ability to change carriers, the added capability or whatever else you want your iDevice to do, think about what why you want to and weigh the good against the bad.