I haven't noticed it, but my photos usually sit in a frame.

Arash:

If the prints are in a glass-enclosed frame, then that is just where you should notice the outgassing most prominently, particularly if the prints aren't matted. The problem is the slow evaporation of the ethylene glycol ink base.

Epson recommends placing paper over a printed image for at least 48 hours before framing to wick out the glycol: http://www.epson.com/cgi-bin/Store/EditorialAnnouncement.jsp?oid=61412340
I think the problem is worst with RC papers such as Premium Luster.

Jim

A slight tangent, but possibly worthy perspective applied to lizabeth's opening question "which of many papers are 'best' and should I use..."
Might I suggest there's a loss of fundamental focus that needs to be applied: First, foremost and always - image quality itself.That's what is important. "Add on's" or so-called "enhancements" (the tons of photo stuff sold, hardware and software that promises "better"), the list is never-ending. Even various photo papers. Similarly, the too-widely accepted thinking "shoot anything, I'll fix it later in Photoshop."
And cows can fly!