I think the XA20 is the pack I see the most at races, particularly at the WT. My wife uses it and loves it, as well (I think it is the men's also).
Last year at the WT I used Salomon's 10+3 Vest pack + their 5L chest pack which worked well, but at the end of it I had 2 complaints. The mesh making the vest is hot (even when I wear it without the chest pack) and it moves around a bit more than I would like (even though it is not supposed to). I also had it 90% full which really did not permit me to carry anything extra from team mates if necessary.
This year I went different again and picked up the Salomon Skin Pro 14+3 (
http://www.salomon.com/caus/product/skin-pro-14-3-...) and then added clips to the front for my chest pack again. So far, I'm loving it. The fit is awesome once you get it dialled in, took me about 30min of fiddling with those velcro shoulder straps (run, re-adjust, run some more re-adjust, ride re-adjust...), way more breathable in the chest area, doesn't bounce...
If I was to change anything on it so far it would be to add an internal pocket or two inside like the XA20 and one with a zipper.
I've used it on every trail run, men bike ride or paddle since April (2-4x week) and loving it.