I'm wondering if working with rails (3) is a good idea when a huge/ugly legacy database is already there (Oracle, SQLServer).
I only have experience with ActiveRecord, is there another ORM more suitable for that kind of job?
Cheers
ActiveRecord can still do the job - for example there are directives that can be applied within your model that make non-conventional table names, primary key names (multi-column PKs, if you have them, used to require some additional work, not sure how true that is in AR3).
For both Oracle and SQL Server you're going to need to get the relevant DB adapters; I don't think either is bundled with AR.
A lot of legacy DB Rails work only needs read-only access - if that's the case - and you can get access to do so - then you may find that defining views that are more "AR-friendly" and referencing those through your models may make life easier. If update is going to be necessary then either a useable primary key will be needed or you'll have to consider dropping down to building and executing custom SQL, something that's fully supported in AR for occasions when the abstractions can't cope.