I usually only care about loot that will help my raid team get further - it's very rare for me to covet gear for the looks, prestige, etc. Sure, we all like having shiny purples and having people admire them, and while I do prefer to look nice, my priority is always to improve my gear for my team, not really for me.
I have never had a full set of anything though - I only ever got a couple of pieces of Cenarion, one piece of Stormrage, and I never had a chance at Dreamwalker. Even the dungeon sets eluded me. I had T4 antlers, T5 shoulders and pants, but never a full set.
Finishing my Tier 6 set was what I really wanted to do before WotLK, and I'm so glad I did it - and just in time. I think I earned it this year.