Okay, iPhone finally booted up after sitting on the apple logo screen for what felt like an eternity. It always gives me a scare everytime I'm stuck on the apple logo, although the phone always eventually seems to boot itself up from this stage (I believe the system is doing some kind of cleaning of trash files during this time?).
Like others here, I noticed I'd lost cell service after rebooting, but disabling then reenabling 3G and edge through SBSettings seemed to fix things.
So anyone else having problems with this update, take heart, and don't rush to do a restore. This doesn't appear to be anything fatal.