On the Irish Moss. I've done a couple of batches with it and a couple of batches without. I'm finding the big difference is in cooling the wort and separation of the trub from the wort. When I used the Irish moss, I had a lot more trub fall out while cooling in the boil pot and therefore had a much cleaner yeast cake at the bottom of my fermenter. In the end, this will lead to clearer beer a little faster, but I'm not really noticing a huge difference at this point.
Direct comparison is an Amber Ale kit I did twice. First without moss, second with. The one without took about 4 weeks in the keg to become nice and clear. So far, the one with Moss has been in the keg for 3 weeks, it seems clearer that no moss at 3 weeks, but still isn't crystal clear. So for me, it looks like 4 weeks in the keg, cold is going to be my magic number for nice clear Amber Ale. Although, Like I said, it seems to be doing a better job of gradual clearing. The non-moss one seemed to make a more drastic clarity change between week 3 and 4. And although not a drastic difference, is enough to keep me using moss from here on out. As I said, in my experience, the biggest thing is in the clearing of the wort, before it goes into the fermenter.