It's just an easy way for anyone to make custom ROMs themselves.
I moved to Oxygen 2.3 ROM. Amethyst was great, better in fact in terms of performance, but there was some bugs that just weren't getting fixed (echo in calls), and the dev had gone AWOL. I tried going to a Desire HD ROM, but I could never get them to boot no matter what I did. Tried various kernels etc, wiped phone multiple times. Even changed to Amon-RA and wiped with that and still nothing.
I don't think Sense is bloated really. I do miss quite a lot of things Sense and will most likely go back to it when a decent Sense + Android 2.3 ROM appear. Sense does run a lot better if you just slap a custom Sense kernel on it though.