I don't think they have shown enough for me to be dissapointed yet. The addition of matchmaking will solve pretty much my biggest complaint with the first game, though. Not sure how I feel about codifying all PvP as 4v4, disappointed in some of the technical details for console and the lack of dedicated servers, I guess, but that's not enough to scare me off.
Then again, I always looked at Destiny as a pretty fun shooter with the structure of an MMO, and it scratched a similar itch for me. I have played and enjoyed a lot of MMOs, so farming, repeating content, etc. is pretty much fine, as long as the gameplay is compelling. On a minute to minute basis, it's more entertaining than a lot of hot-button style MMOs.
A lot of the complaints I have seen about Destiny basically amount to "it is structured too much like an MMO". I don't know why anyone would have expected a total overhaul of the basic game design. I'm hoping it improves and refines the quality and quantity of content, and I don't think we have seen enough of the game yet to judge any of that.
If anything I'm dissapointed by the lack of a new class. I haven't followed carefully enough to know if the old subclasses have been tweaked, either; I would have loved more flexibility in class specialization, although Destiny did a lot of that specialization through gun modification instead of the talent tree like in Borderlands. If they are essentially identical, I WILL be dissapointed, because what is the point of starting from scratch then?