Intellisense would be nice, but only if they incorporate it into Visual Studio too. I have to believe the majority of SQL developers use VS and not EM/SSMS.
I also think Red-Gate has missed a golden opportunity by having SQL Prompt only hocked into SSMS. From what I've read, it was a challenge for them, since SSMS doesn't expose a plug-in architecture. VS already exposes this architecture, so you would think it would be fairly easy for them to adapt their existing SQL Prompt code over to VS.
I could be wrong and perhaps that's one of the reasons Red-Gate is publishing this software and I'm not.