I like my 414, but wish I would have waited, saved, and bought a 424. I plug my Yamaha electric keyboard in two different ways, depending on what I want. If I just want one track, I just plug it right into one of the standard unbalanced inputs. Keep the fader in the shaded position, and use the trim to get the proper level, or you'll end up with to much noise.
If I want to record a stereo signal, I plug into the 5-6 or 7-8 input with a trs stereo cable, and record on two tracks.
So far I've had good results with any instrument or mic when I'm recording carefully, and not-so-good when I'm sloppy. I ususally see them advertised for $299, sometimes $20-30 less on sale or at some of the online retailers. I think it is a good deal, and it is a great learning tool, but for a little more you can get better tape or digital.