I eventually flashed my n810 and installed a-gps. I use maemo-mapper only and the fixing time seemed much better than usual (~30" instead of 4-5minutes). However, I used to experience surprizingly fast fixing times, so I'm not 100% positive yet.

There is no feedback whatsoever, so it's difficult to tell what the a-gps app is doing... downloading something? storing something? I hope it will be more verbose in the future.

I wasn't sure, so I took no risk and started both a-gps ui and maemo-mapper (no fix inside my building) and then I went outside (with no wifi)... Should I keep a-gps running until I get a fix? should I start maemo-mapper+gps while a-gps-ui is running?