There should be no problems other than the inconvenience of having to restore your iPhone to factory settings.
Except for one factor - contacts, calendar, notes, photos in the camera roll. You need to copy all of these to your computer or you will lose them. The easiest way is to sync these with apps on your computer such as MS Outlook or iCal and Address Book on a Mac. Photos are copied the same way you would with any digital camera.
The alternative is a 3rd party app that can copy files from an iPhone to your computer. iOS Data Recovery software is probably the best. It is not free, but has gotten positive reviews.
NOTE: I have no connection with the developers, and don't even own it.
Read more here: http://support.apple.com/kb/HT1414