It looks like rgbyhkr is even tougher than I am when it comes to choosing electronic devices. I am an Electrical Engineer and I am extremrly picky about quality and how something performs.
But, I believe I understand why he returned the MX-900.

However, the need to triple press a button very quickly is probably something that most users will ever have a problem with.

I own a Sony RDR-HX900 DVD recorder with a 160 Gig harddrive and also have the single, double, and triple fast forward and reverse search buttons. Although I rarely use the triple search because it is way too fast, there is no need to depress it three times very fast. It still works pressing it three times at a moderate rate of speed.

I also tested every remote I own to see if I could input three very fast button pushes in a row. None of my remotes could register more than two hits when performed very fast.

In conclusion, I do not feel that the slower reaction time of the buttons on MX-900 will be a problem for most users.