I REALLY hate ads on web-based gmail client, but I suppose they are a necessary evil.
The an ads-removing feature send the wrong message.
I may buy (or donate for) a gmail-client-enhancer. I may buy (or donate for) an ad-remover plugin (well, I already use ABP and ghostery, and donated for the former) But I wouldn't give money for a gmail-specific ad-remover, that doesn't feel right (even if I am using ABP, maybe the 'specific' part?)
I may be wrong, but distributing it at two separate plug-ins may be better. Removing the "ad-removing" part would be the easiest way, because interested people almost all already have ad-blocker.
Even if you chose to let it in, not making it a major marketing point would be smarter. just let it there as an option (activated by default or not, I don't know).
PS: Attachment icons would be real nice, though, I love that feature.
PS2: Yes, I know, using ABP and not wanting to pay for that app because of this feature sounds like hypocrisy, in fact it is, but that's how I thought about it (I have build-in hypocrisy), and I may not be the only one.