Gabe at Penny Arcade got access to a pre-release unit and just posted a review
Penny Arcade - Surface Pro 3
Confirms 256 pressure levels but says its not a bad experience, though he doesn't recommend it overall yet due to other performance issues, it will be interesting to see how MS responds... I wish quite frankly if this was such an important market to them that they got feedback sooner than a few weeks before the device ships. Though it feels to me like they're hitting more integrated GPU issues than anything else, which really falls on Intel.
The main performance issue he mentions is actually the N-trig hover lag, which you can see in the first video that appears if you search for "n-trig lag." This comment makes that clear:
Working on a comic strip, It feels like I’m dragging the cursor through syrup. Strangely that lag doesn’t seem to be present when I’m actually drawing with the pen touching the surface.
Here's the video demonstrating the issue (I think this has been posted several times, but here it is again anyway):
[video=youtube;wYBstWuXtdY]http://www.youtube.com/watch?v=wYBstWuXtdY[/video] ). I think this video's been posted several times but there it is again.
As I understand it the pen goes into a lower polling rate when it's not actually in contact with the screen to save battery life, but the result is that when hovering the pointer lags significantly. Once you make contact with the screen the polling rate increases and the lag is similar to Wacom's digitizers. Personally I find that hover lag to be quite annoying, but the trade off is that N-trig's current generation digitizers are far more positionally accurate than Wacom's old "Penabled" tech (what they sell to 3rd parties). So if you can learn to ignore the pointer and look at the pen tip you can get very decent results. It's probably a better experience over all for note taking, but for Photoshop work ignoring the pointer is possibly more difficult.
Anyway the point is that a faster CPU/GPU won't help that type of lag, it's simply the nature of the technology. He mentioned some other performance concerns which are most likely related to the HD4400 and that higher resolution screen ("Moving around the image also feels slow with some stuttering and screen tearing."), but the cursor lag isn't related.