I'm a practical gal, and don't consider myself one that would automatically gravitate towards "Bigger is Better" theory, but think most of the statements here are true. You do get use to the size after a time.
I recently upgraded my bedroom tv from a 20" tube to 37" LED tv. At first it was wow, now it's just really nice and maybe I should have gone one size bigger. But I'm still glad I went with the 37", b/c any bigger wouldn't have looked right in my room.
For my LR upgrade, I first wanted to upgrade from my 32" CRT to a 46", but I quickly squashed that and decided on 55". My viewing length is about 10'. After looking at 55" the last couple of months, that size seemed a tad too small as well. I know a 60" would be a awesome upgrade. I'm about finished on working on my new 60" center, and it would fit it perfectly.
I was worried about the PQ not being as good on the 60", but I haven't been able to discern the difference between the 55 and 60" tv of the same model. Actually, I thought the 60" looked a tad better, possibly b/c they were produced after the initial 55 launch. (Tvs are launched in order of their size mostly.)
However I did notice that the 60 or 65" D8000 looked way worse than the 55" (at least the one I saw).