I agree with you on the PocketNES emulator, its just soooo good!
However, I always had a soft spot for the Spectrum, so the 2 available speccy emulators excited me more.
ZX Advance is quite good, but you need to make each spectrum game a self booting GBA file.
Foon is a better one, but its not finished, the system menu has very little working, but I think overall its a little more polished than ZX Advance.
I'm also looking forward to the PC-Engine emulator but I dont think its playable yet.