I'm using a LSM303DLHC and I have the compass calibrated. It appears to be pretty darned accurate here on the counter.
I can't seem to find much on how to calibrate the accel or if it needs to be.
I've also done quite a bit of searching to find out how to compensate for tilt. This makes me wonder if this is being done in the library and being returned with the calibrated heading???? If this is the case, it makes it a sweet unit to work with.