Many of my piano teacher friends (who are excellent pianists) own digital pianos along with an acoustic piano and they love and use both of them. For a piano teacher, having an acoustic & digital piano can meet a variety of student needs as well as expanding the musical horizons of piano teachers. As far as mechanical and electronic reliability goes, my experiences have been very good for both acoustic and digital pianos, as long as they are the higher quality brands. You just have to be sure it's a good name brand and that you take care of your piano. Off-brand pianos can sometimes be high maintenance and unreliable based on my experience with them, so be careful to stay away from those brands which include Williams, Suzuki, Artesia, Adagio, and others.
If you want more info on pianos or would like to find out about purchasing one for LOWER than internet or store price, please contact me at firstname.lastname@example.org or call direct at 602-571-1864