The first time I tried starting the android emulator, I quit it and never used it again. Starting up took about 5 minutes already and it wasn't too responsive afterwards. Now Matthew Casperson posted a nice howto for using the snapshot feature of the android emulator to start it up quickly. Now all I need is a trick to have it running faster as well... But that's not going to happen as long as it relies on qemu to first translate everything from x86 to arm code. ;)
Being based on Java, you'd think it would be possible to create a much faster emulator by just leaving out the arm cpu emulation. And it seems some people have done that with youwave. Unfortunately, that's windows-only.
Another line of improvements would be to speed up the graphics, as reportedly displayed with impressive results at Google I/O 2011.