DDI tools are one of those things that I would definitely have to try before I would buy (or rather buy monthly.) My concern right now is that Wizards will try to kick in their subscription model before anyone gets to really use the creators, generators, and game table in full for at least a little bit.
It sounded really good when it was going to be a free trial period, and the assumption was that it would be a full free trial period. But now, based on what it sounds like to me, by the time that they have their applications figured out, they'll have moved to a subscription model, and the free trial period will have just been the Dragon and Dungeon articles, plus the rules compendium (which is basically just a search function for our books until a lot more rules come out from different sources.)
I'm sure they might offer limited samples or previews, or free features with limited functionality once the tools are ready to launch, but I'd be wary of basing things off of that. The character generator that came with the 3.0 PHB was pretty good for what it was, but then look at the flop that was Master Tools.
I'd want the chance to use the finished product for a little bit before shelling out $15 every month... and that's what they made it sound like, originally. (1. DDI will have these features. 2. DDI will have a free trial period at launch. There's a very clear assumption there.) Whether it's due to technical difficulties or not, it almost feels like a little bit of a bait and switch at this point.
And no, I'm not saying they are greedy, mustache-twirling villains... perhaps Hasbro asked Wizards to go to the subscription model before the first supplements come out so that everyone isn't getting free Swordmages or something (and that makes sense), even though the tools won't be ready. But that's not what everyone thought this free period was going to be when it was first marketed.
So I guess I'll wait and see if I have the opportunity to try it out. Otherwise, there are plenty of generic free tools out there I can adapt and use.