It might appear duller as the brightness might not have been on full? (I've compared my mini to a full size iPad and it doesn't seem dull so it might just be that).
Whilst it is only a little but more, you need to think about form factor. The mini is much smaller and more portable. You won't even notice the pixelation after a few hours use. I've got a retina iPhone4 and the mini and I don't go form one to the other thinking it is an inferior screen (same goes for the full screen iPad... I don't even think about it now).
Edit... If you have an iPad2 then going to the mini would be an improvement screen quality wise due to the smaller screen same resolution.
not sure about "dull" but when I looked at a Mini in the store - the colours seemed more muted and drab compared to my wifes Ipad 3.
I didn't buy one - going to wait for the Retina version - which will then be almost the perfect tablet IMO
atm I'd buy an Ipad over a Mini - for my uses