I am about to launch a beta site, and heroku looks like a great option. The only think that is getting me down is that the only search option is $20/mth for the Websolr
If you're using Postgres for your Rails app then take a look at this free way to do full text search:
Part 1 and Part 2
This uses the pg_search gem to allow you to use PostgreSQL's pg_search_scopes feature and have full text search without any other dependencies.
pg_search
pg_search_scopes