Got Matt3o's prototypes in (4-color pack). I have to say I'm mostly impressed with the quality of them. My white spacebar did come in noticeably warped, and my black one ever-so-slightly warped. But that is mostly in the nature of them being prototypes. I did have to shave of a little off the bottom of the bars to even them out, since there were some plastic pieces hanging off the bottom that caused an atrocious sharp ping off the plate of the RF. And the black bars had a little swirl in them on the sides (mostly the rear where you couldn't see them) But like I said, these are prototypes. They are bound to have problems as prototypes.
After doing a little doctoring, and using the other three usable bars, I have to say I'm incredibly impressed. They have a slightly rougher texture on top, one that is more similar to the regular PBT alphas that you'd find on a Topre board. It is VERY pleasing to touch, and not slippery at all.
Also, the sound. Oh god, the sound. After a little bit of doctoring, they DO NOT PING LIKE THE ABS BARS DID. Nice. NICE healthy thock. I cannot stress this enough. If you've ever used the ABS bars on a Realforce (I cannot say anything about HHKB/660C since I don't have them), there was always kinda a ping on the downstroke when the ABS spacebar hit the backplate when bottoming out. At least that is how it sounded like to me.
In regards to color matching, the white and the blue (based off what I remember when I had my blue RF set before selling it) are incredibly well matched. I couldn't tell the difference from the colored Realforce sets and these spacebars if I tried (and I'm not colorblind). I don't have a red RF set to compare them to, so I can't tell. The black is such a sumptuous black color that I've actually taken to using it on my board, over all the other three colors. I cannot compare this color matching either, but you can see Matt3o's previous picture about them to see that color matching.
Overall, this is just my review and 2 cents from the current prototype bars that Matt3o was selling over on DA. But I honestly cannot wait to see the production spacebars. Since those are most likely going to be significantly more polished than these.
I'll try taking some pictures later on once my camera finishes charging and edit this post.
