Skype over 3G and Tethering still work properly. iPhone 3G v3.0 (7A259g) has been unlocked and jailbroken. See the video below: 

Apple iPhone 3G Unlock Adapter V5 for Version 3.0 (7A259g) Beta 2 Firmware 04.22.01

Along with the SDK, iPhone 3.0 Beta 2 Build: 7A259g is also released.  It comes in at 228 MB.

We are, as you can see, downloading them both now and will report on any improved snappieness™.