I've been using Tracktion for about a month now and I really dig it for many reasons.
It has it's problems, but the pluses out-weight them all. It's very stable as compared to N-track (for me), it's efficient on my crappy old computer, it was simple to learn, tracking is a breeze. Mixing is easy enough.
I agree that a mixer would be nice, but my mixes in Tracktion are better than they used to be in N-track, maybe it has to do with something else, but tracktion really causes me to listen more rather than look at numbers and meters. It used to be that when I recorded tracks two guitar tracks I would pan them the same number value, opposite ways, and have them at the same level, at first the volume adjustments in tracktion bothered me, but now I'm used to it. I know this is my problem to begin with, but I do kinda feel like tracktion just makes me concentrate more on listening rather than seeing. Things that used to bother me about it, I now like after a month, like for example the waveforms, they kinda suck (they were great in n-track), but this just causes me to get away from trying to fix things in the mix and track better.
Keep in mind I'm purely into recording bands, I have no desire to use MIDI, and although I guess it would be nice to know more about it, I just can't see myself ever wanting to. Most complaints I hear about tracktion are due to MIDI stuff. The tracking is tracktion rocks, enable the inputs, point them to the track you want to record onto and do it. Not that N-track was rocket science, but it took more thought and time.
Editing seems a little different, but I don't do that much either, if I need to edit something I'll generally just re-record it now.
I hate to sound super cliche, but tracktion ain't about the features, it's about making music easily.