Trotta, jailbreaking your phone isnt illegal anymore, just gives you the freedom to change your phone to how you want it and some of the packages you can get through cydia are awesome. It only becomes illegal if you download paid for apps for free, but how they gonna know :p
It does say that if you go to the apple shop with a jailbreak that it will void your warranty but if you do a clean restore before taking it there, they wont know it had been done.
The trick is to back up your phone on a regular basis, just in case.
I have had no problems whatsoever doing mine and it was really easy to do as well........FREE YOUR PHONE.
My oil light came on last night as I went round a corner, thought the engine sounded a little tappity. All topped up again now and nice and quiet again
