Natty hasn't shipped yet; in fact, the first beta of Natty hasn't come out yet.
2.6.38-rc2 is available from kernel.org now (and is doubtless in the Ubuntu kernel PPA already); I compiled it on openSuSE 11.4 x64 MS5 two days ago! (Two hours and sixteen minutes of compile time on a Celeron DC E1200 - but decidedly worth it.)
Turns out there is little reason to wait, and *especially* if you have an AMD GPU of HD5xxx (if not HD6xxx) vintage; however, in order to take full advantage of that latest kernel, you also need X.org in the 7.6 series and at least 7.9 (if not 7.10) of Mesa.
Thanks, good to know 2.6.38 is on the table.
I asked cause this part of the article made me think Canonical already decided to stick with 2.6.37:
Even if Canonical does decide to stick with -37, that's what the kernel PPA is for.
The -38 RCs are also making noise at other distributions (I found out about it on the openSuSE forums, and have -38rc2 installed in my MS5-based setup, and I would think the same is doubtless true elsewhere, especially over in Gentoo/Sabayon-land), primarily because of the increased support for KMS over and above even 2.6.37. However, throw in the kernel improvements with those late-breaking improvements in X and Mesa (most of which just missed the earlier code freezes, especially those in Mesa) makes it all the more important that they be used in tandem.