Thanks guys.
Just to clarify, I've been watching the same HD cable channels including watching the Mets' annual swoon and the grainy quality is consistent across all HD channels. Normally the channels vary from good to very good (Mets games in particular look very good) to the point where they yield that "looking out a window" experience, but that is gone as of the past few days. And yes, my plasma is 1080p so fortunately I get to see the full reduction in my picture quality.
I called my cable company last night and found out my cable signal is on the weak side, so I'm hoping that turns out to be the culprit (that or a bad cable). Of course being home from 8 to 4 during the week to get it fixed is a bit of a problem. He all but laughed when I asked for a Saturday or Sunday appointment. I love cable.
Swampwalker -- I've seen the effects of clouds/snow/rain on satellite at my brother's in Annapolis and my friend's in Chicago, and it was all too frequent and not fun. My brother also ditched satellite because of it. Thanks for reminding me, but we're surrounded by huge trees so it's not even a possiblity (none of my neighbors have satellite either).
I'm seriously thinking of giving Fios a try. I know they have their service issues as well, but from what I've seen their picture quality seems pretty good. I'm a little concerned about their internet service though, and I'm not sure switching from a cable company to a phone company will make me better off overall. Any thoughts/experiences with them vs. cable?