Really depends on what you expect your use case to be, and the applications you intend to use on the server.

I used to use the N810 as a VNC remote to a Mythtv box (works great upto 800X480), and also played with the tcp/ip interface. The Mythweb package works well with the N810 standard browser. There is a "mobile" style web interface called mythmagic which should work well with the N810 - I have it installed on my server so I will give it a go..

For a tivo there is a remote called pyTivo, which should work quite happily on the N810 as it uses Python, and no fancy graphics.

Also fairly sure that at one point there was a fairly nice remote to Windows Media center although it is probably depreceated now.

not sure about XMBC. There is a remote for the N900, but dont think it'll work due to the QML version required.

for Music playback, the Squeezeserver and players are nice. Squeezeserver is a free opensource webserver, and the interface has a skin designed for the earlier Maemo tablets.