
I'm typing on a TypeMatrix-2030 (first generation) in Dvorak for several years now and I have grown attached to its matrix layout. While it has quite decent double-scissor switches, I was wondering how a mechanical version would be. So I got a (two, actually) Tipro MID-AM-KM128A-016 programmable POS keyboard (with Cherry blacks) from ebay and gave it a go.
original tipro:

Rearranged the keys to TypeMatrix layout and programmed the controller. Then I had to print, cut and insert all paper labels for the re-legendable key. Annoying work

Unfortunately, these flat keys just aren't made for typing - it was horrible. So I replaced the letters with keycaps from another board. Well, somewhat better but QWERTY keycaps arranged in Dvorak layout make for a bumpy typing experience

with QWERTY keycaps:

Finally, the QWERTY keys got ditched and I inserted some blank keycaps (blue POM jelly caps):
Here's the more or less final version:

My verdict so far:
OK for fun but not for serious typing because:
-Cherry Blacks are not my favorite switches...
-the segmented space bar (all the 10 keys) is kind of annoying
-<enter> and <backspace> (the yellow 1x2 keys) span two switches which makes them hard to press
On the plus side:
+matrix layout

+completely programmable in 4 layers. The small, green key in the lower left corner activates layer 2, a numpad. Also, cut, copy, past, Alt-Tab and Win keys.
Cheers!