Before you hit that 'Upgrade' button, here are a few items of community interest to consider.
1. It's a one-way street. You cannot downgrade the firmware back to 1.0.2, not even using the alt-Restore trick that lets you pick an ipsw file to restore from.
2. The new firmware is locked down tighter than a WWE Half Nelson. If you somehow managed to upgrade while keeping your iPhone apps intact -- I have yet to hear a confirmation of this happening, and I kinda doubt it can happen -- congratulations. Everyone else is out of luck. Don't expect a jailbreak anytime soon.
3. You can buy songs at the iTunes WiFi music store and transfer them back to your computer. iTunes creates a custom playlist with your purchases.
4. The Home-button and double-space tricks are cool. Not sure whether they're cool enough to make it worth cutting off your access to third party apps, though.
5. My media folder disk access utilities still work. So if you want to store some files on your iPhone or iPod touch, download from here. For Intel Macs only. If you want to run on a PPC, grab this universal, rename it to util and replace the one in my tar file. It won't run as cleanly but you still get to use it on a PPC Mac.