Is a screen protector worthwhile for an iPad?
I had a screen protector on my iPad for exactly 2 days.  I bought an anti-glare one because I found that the matte finish made fingerprints much less of a problem on my iPhone.  Unfortunately, I managed to get a few tiny creases when I applied it, causing annoying bubbles.  I found the feel of the touch screen was not as good, and felt the film reduced the beauty and clarity of the display.  

Ultimately I removed it and, so far, I have not gotten any scratches. I do keep my iPad in Belkin Grip Swell case, and put that in a Case Logic netbook sleeve when not in use.  I also clean it frequently with a 3M microfiber cloth.

Pros


Protects your screen (yes, really)
Anti-Glare screen protectors minimize glare and.. fingerprints!


Cons


Difficult to apply perfectly (and less-than-perfect is not good - buy two in case!)
Expensive
Makes display look and feel cheap
Might not really be necessary if you are careful