My initial impressions after about a half day of use:
The spacebar sqeaked occasionally at first but that has actually stopped completely just from use. I can't make it squeak at all no matter the location and speed that I press the spacebar down. If the problem comes back I'm confident that white lithium grease will resolve it.
The surface of the entire keyboard, wrist rest and keys have a soft matte texture which both looks and feels very smooth and somewhat soft/silky. It's similar the surface used on some cell phones. I don't know if there are any disadvantages to this or how it'll wear over time. I've noticed areas on the wrist rest where oils from my skin left an impression but it's not permanent and wipes clean with a damp cloth. Lint and dust particles may stick to the surface a bit but that's nowhere near as frustrating as finger prints, smudges and dust I'm sure you've all seen on keyboards with a glossy black surface.
This is my first keyboard with brown switches and the only other keyboard I've been able to compare it to is the Razer BlackWidow which uses blue switches. If I was looking for a keyboard strictly for typing and didn't have people around me that the noise might annoy, I think I'd choose blue switches, they're excellent for typing. However, I plan to use this keyboard for a lot of gaming in a dark room, which is also why I chose a keyboard with backlighting. My understanding is that it's easy to re-actuate blue switches which can be a problem for gaming. However, for regular typing I'm pleasantly surprised with this keyboard as I can easily pull 100 wpm with it already, and I still bottom out a lot.
The wrist rest is a really nice addition, there's not much too it but I find the angle to be quite comfortable, even though the ergonomics police will slap you across the wrist for using one (my high shool typing teacher would always get after kids for doing this).
The original U9BL keyboard used a shift key modifier for media and brightness controls. Thankfully they went to a Function key in place of the right Win key for the S version.
Also, a few negatives but so far just the nit-pick variety:
I found the backlighting state isn't remembered on reboot (both USB and PS2), my Microsoft X4 didn't have this issue.
The backspace and right-shift key were raised a bit higher than the other keys, even after a good amount of typing as I didn't notice it at first. Just something to watch out for if you pickup this keyboard as there may be a few keys that need to be properly seated.
While they adjusted the legends a bit for better lighting coverage, there are still some keys that are a bit uneven. Since the light is under the upper-half of the keys this is most noticable with the F1-F6 keys where the media icons are on the lower half of the key. There's also a wide horizontal line on the spacebar which isn't fully lit but I don't really mind, it's actually kind of a cool effect. This is also noticable on the Windows key when the lighting isn't on the highest level since the Windows Logo is in the center of the key.
