I just reverted back to version 6.3 on my own iPad 3 with no problems at all, although I did have to install all my music and films again, which TBH didn't take very long using iTunes from the backup.
If you haven't got the 6.3 IPSW firmware file for your particular iPad, you can find it here
Firmware Links - Download iOS Firmware for iPhone, iPad, iPod Touch and Apple TV / Just a Penguin
Make sure you download the correct version for your particular iPad, you will notice the firmware which can be installed are marked with a green tick...these are the versions that Apple are still acknowledging for activation.
After downloading the correct IPSW firmware, attach your iPad to iTunes and if using a PC hold down the shift key, Apple refer to this as the option key, but on PC' s it's the shift key, while holding the shift down click the Restore Firmware button, a box will open prompting you to select the firmware file you downloaded to your hard-drive.
Note. If you download the file with Internet explorer it may have a zip extension, if so rename it so it has the .IPSW extension.
It will then re-install vers. 6.3 firmware, though I'm not sure how long Apple will allow it.
TBH this is the first time I've ever felt the need to revert to the previous firmware, but I dislike Apples choice of colours in v7, and it definitely is slower than 6.3 on my iPad 3 anyway, also some text such as film titles ect don't show up, as white text obviously don't show up on a white background. Colour wise I think it looks worse than 6.3, severe lag in some area's like changing desktop screen backgrounds ect. I know the bottom icon task bar assumes its colour from a mixture of the background pic colours but mine looks rubbish regardless of the background image I use. Anyway.. JMO