I bought Asiatam's from Bill recently.

The Mato versions are cheap knock offs, and accordingly need a little more attention - bending the frames, shiming the gear shafts, make sure that all the grub screws are tightened properly, etc. They also need running in, just like the older monkey metal HL gears.
I've been using them in several tanks since the start of the year and not had any problems that I couldn't fix, but I wouldn't go so far as to say that they are as good as the Asiatams or Tamiya's.

If you can get the Asiatam's I would recommend you go that route, or look at RCC's steel gearboxes. I use the Mato ones primarily because they are easier to get hold of (Mato always has stock, and they are just across the border from me), and the RCC steel gears make tanks like the Tiger way to fast for our club rules