The SD card sticking out is sort of annoying, so I soldered a microSD card adapter directly underneath the R-Pi.
The modification is very simple, you don't even have to care about the purpose of the pins, just line up each contact on the holder to the matching contact on the adapter and solder them together using a wire. Remember to short out the "card detect" pins.
I am using 30 gauge Kynar coated wire, plenty of flux, flux core solder, desoldering braid (in case you screw up).
The wire lengths are short enough to not cause problems. The adapter is still very thin and do not add to the overall thickness of the R-Pi at all. Full sized SD cards will still work after this modification.
I also have a micro SD adapter (was thinking at some point to do something like this) and a card (2GB, no class, not sure of the brand) that did not work with debian squeeze. Just tested it yesterday with the latest OpenElec build and it works fine now.
I got rid of the ugly adapter and added in a proper microSD card holder. It's held in place using double sided sticky tape, which also acts as an insulator. Becareful when doing this because full sized SD cards has two ground pins while the micro sized SD card only has one, don't mix up the signals. Also, this time the card detect switch is wired properly. The holder I used is a Molex brand 502702-0891.
It boots just fine using both full sized and micro sized cards. The main concern was that the asymmetrical wire lengths might cause skew, but apparently at the operating frequency, the effects are negligible.