I enjoyed progression and being top in the server, but they made encounters so easy (Naxx in 1 night? Seriously?) Then you get the very best gear, but its no better than the next guy. Thats frustrating.
As for alts, i had no problem with my alt having gear 2 instances behind current content. Thats why its an alt.
Naxx is an entry level raid. It's supposed to be easy. In fact Blizzard always said it would be. You can get 80 and go straight in naxx.
Ulduar is a different story.
I personally don't consider myself as having a main. I play all my toons. Little bit of this one, little bit of that one. In terms of progression i'm way behind everyone. I'm fine with that. But when you look at PvP catching up is down right painful.