<p>I want to start using Nunit (finally), I am using Visual Studio 2008.</p>

<p>Is it as simple as importing Nunit into my test project?</p>

<p>I remember seeing a GUI for NUnit, does that do the exact same thing that a separate test project would do, except show you the pass/fail visually?</p>

Yes, that's basically it. Personally I find the unit test runner which comes with
ReSharper
to be excellent - and the tool itself is well worth the licence feel. Alternatively there's
TestDriven.NET
.
Having a test project which runs nunit-gui or nunit-console separately is all very well, but you really want the whole unit testing experience to be as seamless as possible. The easier it is to write and run tests, the more likely you are to do it - which is a very good thing. Don't underestimate the gradual build-up of frustration due to a
slightly
poorer user experience, flipping between windows etc.