Although I've never even used N-Track, I have no problems suggesting it for getting your feet wet. Quite a few people that frequent the forums love it, and you won't be out much cash if you don't.
As for the more expensive stuff:
Cakewalk: I've used it a lot for about 2 years, and I'm not fond of it as more than a sketch-pad for audio-- personally.
Vegas Audio 2.0: I demoed it for a couple of weeks with a few complex mixes (no recording... everything I mixed was originally tracked in Cake) and it seems decent. The interface is pretty easy to use and it has a good, flexible buss structure (now that
any DirectX plug-in can be used as a track insert). It's currently my favorite, but I'm sure I'll have more gripes if I start using it on a regular basis

.
Samplitude: I demoed it for about a week (recording and mixing). The interface wasn't very intuitive, envelope drawing behaved rather weird, and "sucks" is the only proper way I can describe the "mixer". There are plenty of really good things to say about it too, but those bad ones happen to be central parts of my working relationship with the software. My assessment: close, but no cigar.
Cubase: I've never even considered demoing it because it requires an annoying dongle. I've heard the results that others have done in Cubase, so I know you can create some tasty recordings with it. I'm also fond of the simplicity in the design of ASIO. Only the dongle kept me from trying it.
I'll echo what TREBLE said about finding what's best for how
you work, and add a warning about being charmed by marketing feature bullets. Lots of stuff looks good "on paper".