A few bugs and performance issues remain, too, so while the phone will be usable, it won't be fast. If you do something unexpected (such as forcing the iPhone off), there is a small chance that you may end up restoring your device. However, it is impossible for any bugs to brick or disable your iPhone permanently.
Finally, media syncing is not working, so loading your media onto your phone is kind of a pain. I'm working as hard as I can, though, and I expect to fix these issues soon.
Required Reading
Start by brushing up on the fundamentals of iPhone maintenance: how to get your iPhone into Recovery Mode, how to put it into DFU Mode, and how to perform a firmware restore from those modes.
The iPhone is a well-engineered device, and it is virtually impossible to brick if you know these techniques. If all else fails, remember that you can always restore using DFU Mode.
You'll also need to be reasonably comfortable working in a command-line interface, and unless you're confident in trying to compile your own binaries, you'll need a PC running Linux (or a Linux virtual machine).