Our mysql database server machines (each of which have more than one mysql server running) are on the same local ethernet (100 mbit or gigabit) as our hosting servers so it is unlikely that it would be as fast to connect to a mysql server on the general Internet. It may be possible to maintain a very fast connection close to our network, but I think it'd probably be a whole lot cheaper for you to get a dedicated server with us if your application is extremely performance sensitive. Server performance may vary quite a bit on a shared system due to all of the other activity going on.
We do aim to ensure good performance on our database servers, though. I'll poke some people and see if something can be done. Also, always remember to optimize your application as much as possible as it will make your site faster, as well as reduce the load on our database servers (if only a little bit). I just checked hobbes and it looks pretty good. The load (on a dual processor machine) is around 1.
- DreamHost Head Honcho/Founder