I have to say that I feel like Rails' ORM does a magnificent job of saving me time. Migrations allow me to write database changes that can be undone more easily.
An ORM also seems to lower the amount of configuration it takes to get development databases synced. It's not as much of an issue for an experienced dev, but a designer or new team member would need help.
I have had to learn AREL, the relational algebra used by ActiveRecord, in order to do more advanced queries. That's analogous to learning SQL in more detail, but I'd still take that in a heartbeat over writing raw SQL. The ORM automates things like tersely expressing the object associations I've built, leaving room for fewer syntax mistakes.
I've not used the Rails ORM so I can't comment on how good it is or how easy it is to debug queries (peer behind the magic).
*The ORM automates things like tersely expressing the object associations I've built, leaving room for fewer syntax mistakes.'
Maybe it depends on the system you're working on however mitigating syntax errors seems like a small benefit. For me the SQL for most projects is fairly static i.e. once a given set of queries has been defined and tested they can lie there untouched, so once I nail a query and it performs the way I like I hardly ever need to go back and touch it again. However the performance penalty of sitting behind an ORM is ever present, for each query (at least for a cache miss). Personally I just don't like having 100s of lines of code sitting between:
model->get(('model.field' => 'value'));
and actually receiving the data.
It just seems so.... unnecessary.
of course YMMV, and perhaps the benefits kick in when you're working in a team (I'm not).