I played with IndexTank a bit this past weekend, and it seems like they are really hurting from lack of a good gem that fits into Active Record. When compared to something like ThinkingSphinx or a project like that it feels very un rails-ish.

I noticed this project has cropped up to try and solve it, which is awesome: https://github.com/flaptor/thinkingtank however it's not Rails 3 compatible right now.

If I were IndexTank, getting a gem like that up to speed would be my top priority I think to get real traction on Heroku or amongst rails folks.