Tenjin started working in Rails 3 on our early projects. similar to nepalez, it went okay until things needed to work for people, not the database. The layers of 'convention' magic simply became more work than it was worth. Testing was cumbersome due to Rails' monolithic structure.
We discovered Architecture: The Lost Years, and fell in love with the hex arch style. Rails at this point was causing more work than it reduced, so it was out. We took a first run at trying to hide an ORM behind a general persistence layer, which did not go well (for obvious reasons). We settled for the slightly more flexible DataMapper for the time being.
Our focus turned to simplifying the rest of the architecture, switching to the lightweight Sinatra, which made our views dumb data-displayers. Shearing off the the core application logic into user story orientated functions (rather than CRUD/REST), meant that we have meaningful first-class core behaviour defined. Only the persistence layer remains to be de-dunked and re-worked.
Learned about ROM from a former colleague, though I don't know how he knew about it. The philosophy and implementation direction matched what we need. At the time, it was just a little too green to use in production, but that was before the advent of Repository. Excited for the next project that I can test drive it on. If it goes well, we may make a big push to standardize all of our existing code bases to our new Dirt style, including ROM.
Cheers to solnic and others for the research, work, and even moreso the open mindset. That interactivity and willingness to hear others out creates an infectious energy, and that's what got me boosted from interested to helping (in as much as I can, anyway).