Could I use a 2010 kernel in the 2009
I don't know how well the new kernels would work in a 2009 setup, if at all.
But note that the 188.8.131.52 kernel I mentioned before was built for a fully updated 2009 system, and at least on my 2009 install it works very well. (It's actually also a 2010 kernel: the package is called kernel-184.108.40.206-pclos5-1-1pclos2010.i586.rpm
I don't know how long it will be available once 2010 final is out, but I just checked a number of the repository mirrors and found it on every one of them except the main one (ibiblio).
(For Synaptic to find it you have to add "testing" to the Section(s) line of your chosen repository before you hit "Reload". And remember to remove "testing" when you're done.)