First - let me start of an say, as a pretty regular user, that I think you guys are doing an amazing job. This application has come so far - it really is a challenger to Photoshop!
Now I do have one feature that I need to 100% switch over.
Guides. This is the most critical feature, as I am often cutting up an image to make a website and guides help me to more or less lock the pieces for cutting and pasting.
Other than that... the other thing I would consider is applying effects to layers (Maybe just drop shadow, glow, color overlay and emboss. PS didn't really get into this until version 6 or so... and it is really nice to be able to expand the effects on a layer an easily turn them on or off... or add new.
I just downloaded 3.0A1 - so far... I am stunned.
Keep up the great work.... VX