Finally! - found some sensible discussion and suggestions about these issues!
Had my X1 for a few months, and been really disappointed with the signal issues (my reception is OK, but not great, and the X1 issues just make it worse)
I can also confirm that it appears to be related to the lower part of the phone: swapping between holding the phone 'normally' (i.e. with the bottom of the phone cupped in my hand) and holding by the top can change the reception by at least 2 (and sometimes 3) bars.
(I tried to test the 'contact' theory, but found similar changes when just holding my hand very close to the case without touching it - so I can't offer any suggestions there).
I know the bars aren't the most accurate way of monitoring signal strength, but I think that 2 or 3 bars change certainly indicates an issue!
I can only assume that the X1 designers intended the phone to be held in some other fashion - because I also have an issue that whenever I hold the phone, I find I am covering the loudspeaker with my hand / fingers - why is that near the bottom as well?
(on the subject of case design, why is the USB port on the side at the top - why not put it on the bottom so someone could make a cradle for the X1 with charging built in?)
Question for those of you that have dismantled the X1 - is there any possibility that the screen could be removed and re-assembled the other way up (so that the antenna ended up at the top?) - I know it's unlikely, but it would resolve some of these issues.....
I guess I'm going to have to learn to hold the phone delicately by the top edges (and hope I don't drop it!) and see if that improves the general reception....