Yes, we use and find it extremely useful.
In our case, we are a (very) small team that supports a database that is vital to company business. Our code base is pretty complicated for what it is (C++ on top of SQL) and we don't really have the resources to make any large efforts to fix things. Instead, I've been coming up with ways of improving things with what we have.
I tried the Visual Studio Team test edition (or whatever it's called), but I found it to be a bit too much of an effort for our resources. Instead, we chose TSQLUnit and modified it a bit to serve our purposes. I essentially wrapped its functionality so that we could run the tests as a nightly job and send a summary email if any failures were found.
Next we just created unit tests (stored procedures) when we identified something in the system that we wanted to catch. Most times it's a small issue that ends up rolling into a larger issue if left unchecked. A lot of times it's something that we can't fix with our client software, so it's been a big help.