Using a tool to beat match has always been considered "cheating", but it is obvious why it is a tool. Beat matching is probably the most technically challenging aspect. Eventually, you'll even get a feel for songs that are close in tempo--most music in a genre will be pretty close by default. Learning to ride this bike with training wheels is just an option I did not have. Being able to manually adjust the pitch/tempo (depending on equipment) without the auto tools becomes quite satisfying.
Some DJs talk about knowing what key a song is in, and if it will mix into another song. If you then have to adjust the pitch for beat matching, how does that affect the key of the song and how it now mixes? I've never claimed to do this, but after playing in school band I can at least hear the wahwahwah from something being out of tune (or was that the nitrous??). Maybe if you're mixing some prog-trance with sustained chords you might hear that, but I'd suggest finding a different place in the track to be mixing.
The physical controller is precisely why I love vinyl.