My N810 finally arrived yesterday, and after working out how to get the battery cover off, I got it up and running with the 48MHz kernel (The N800 and N810 use exactly the same kernel, so just use the one I already released here.
I’m happy to report that the on-board eMMC is happy to run at 48MHz and performs pretty respectably with transfer rates of about 11.5MB/s compared to just over 13MB/s for the fastest card in my collection. As previously discussed, you need to force the CPU speed up to maximise transfer rates.
Other people have also said this, but if you make a backup on the N800, you can restore it on an N810 without any problems. Just remember that if you had the fmradio app installed on the N800, there’s no radio hardware in the N810