The pixels will make you regret it.
I dunno, I never thought it was worth it to upgrade the iPad 2 to the iPad 3 for the Retina alone. I am still unsure if I want to upgrade my iPad 2 for the 4. I am tempted to continue waiting to see if they alter the form factor with some extra additions in early to mid 2013... I wouldn't mind it being lighter. but its not necessary.
It depends on the user whether or not the PPI matter.