IF you're on 3.1.2 or 3.1.3, then i say yes. IF you're on 4.0, forget it
i ran into some major issues last night, tried to downgrade from 4.0 ended up in a reboot loop for a while then just decided to go with a vanilla iPhone until the next 4.x OS
4.0 on a JB 3G is way too much micromanaging for a slow and laggy device, imo
i really hope the next OS is more 3G friendly