I apologize for the length of this post, I just had to post my appreciation of this amazing piece of work.

I upgraded 9 days ago from KP49 after reading through many dozens of posts to make sure I wouldn't run into any problems.
I'm not using the FM transmitter boost program, nor am I (currently) using any of the boot menus available or any battery patches or other such tweaks, so I went for it - and I couldn't be happier with my N900!
The upgrade could not have been easier, and the difference in smoothness is staggering!
Seriously, a kernel change should not make this much of a difference!
Of course, I'm running CSSU Testing (21.2011.38-1Tmaemo3.1), so I'm sure that plays a huge part too... likely the difference I'm seeing is due to the combination of the two.
That said, the difference wasn't truly noticeable until KP50.

I've noticed a reduction in battery usage, though I haven't measured anything so I can't provide hard numbers.
Another thing I noticed is the swap usage is considerably less over time than I previously had.
I've always noticed that when my N900 was lagging badly (like when trying to answer it when ringing), I was well over 200MB into swap. It seems 210MB is the magic point where it is downright painful (and embarrassing) to use.
I do tend to abuse it by leaving too many browser windows open at the same time, on pages I want to go back to and read later. Due to the way many pages are written, I usually end up with creeping memory usage until the phone is almost unusable.
However, after this upgrade, I noticed it seems much less aggressive at swapping out apps. When I expected it to be nearing 200MB, swap was only at 157MB. I noticed today a slight bit of lag when unlocking the phone (I do use the numeric lock), and I just looked (with 11 windows of various apps, including the browser) and I'm using 218MB of swap. I'm quite surprised as at this point it used to be painful switching between apps... it's not!

So, in short - if I had more time I'd be digging through your patches as I'm curious what kind of changes you made to make this dramatic an improvement.
I've been considering the N9 for a while ('cept it still costs too @(#& much for a device with no warranty in the US), but now I think I can hold off longer (the other problems can't be fixed by software changes, the screen is too small for my aging eyes and the poorly-designed proximity sensor is too sensitive for the heavy IR in S. Florida).

I haven't overclocked since KP47, I may just try it again with this kernel.

Thank you very much for making my N900 feel better than brand new!