Unstatisfied
I am one of the few votes for "very unsatisfied" above. I recently canceled my subscription actually.
One of my biggest complaints follows what most other people have pointed out; the horrible login system. Logging me out every 20 minutes is extremely annoying, most especially when I am in the Compendium and have to go back to a different window to log back in.
But more than just the annoyance, the login system exemplified the hard to use/poorly designed nature of the entire D&D website. Why, as a paying customer, do I get shunted back to regular D&D website when I log in? Why do I not have a portal that points me to my special DDI content? Why does the compendium insist on opening in a new page? Even if I am just browsing as a non-DDI person, why is it hard to find the area where the content I am interested in is located? (Good luck finding the errata without using the link in the Q&A (also good luck in finding the teeny tiny link to the Q&A archive once that question moves on))
The D&D website seems dated in its design philosophy and something that was slapped together. Hell, even this forum has a "Remember Me" option.
I was underwhelmed by Dungeon, although I did enjoy Dragon (even the preview articles).
I was also pretty impressed with the Character Builder, but the lack of easy to implement house rules made it useless in the game I currently play in.
If I was DM'ing, I probably would've stuck with DDI, but I just reached my breaking point with the website. If they redesign it/implement all the things they promised I may look at it again. But for right now, it's not worth it for me.