If you fly a lot of coach segments on NW, America West won't scare you at all. A lot of newer Airbus aircraft flying the line, hard-working staff on the ground and in the air, and transferring at PHX is easy if sometimes a bit of a hike. I flew 30+ segments with HP in the 2003-04 period and never had a cancelled flight or missed connection. I think they have some extraordinary employees.

Being NW Silver Elite gets you nothing on HP, though, and you don't earn NW miles unless the flights are official NW/HP codeshares.