Not really worried about it, to be honest. Does it NEED to have it for you to enjoy?
Of course not, but with all Bethesda's talk about how impressive their new engine is, it can seem just a tad dissappointing when it's still behind many other games in some ways. I mean, I don't expect Skyrim to have the best graphics of any game on the market, but what we're talking about here is an effect that a fair amount of games are doing now, and at least some of them are multiplatform or console games.
I hadn't paid that much attention to the lack of SSAO in the screenshots at the moment, but now that you mention it, yes, I'm not seeing it. Kind of dissapppinting, but its absence never quite jumps out at me like a subpar model or texture does or something like that. It's one of those things that's nice to see, but I can live without if it's not in the game, though it's a minor dissappointment if the engine doesn't support it.
its fine game-play is the most important thing
I agree fully, but just because something isn't the most important thing in existence doesn't mean it's not desirable. If that were the case, there would be no point to video games at all, because they're by no means essential. No one ever said gameplay isn't important, here, it is, but that doesn't mean it's the only thing that matters. Good graphics, like good sound or a good story, is not the most important thing in the game, but it can improve the experience and make it even better than the gameplay alone can make it.
I'm not saying ambient occlusion is prohibitively expensive to the extent that it's impossible in a game like this. But it very well could be in this case for all we know as of now.
Considering it's been done in both Morrowind and Oblivion with their respective Graphics Extender plugin, it may not be as impossible to know its feasibility in a game like the Elder Scrolls as you might think. Admitably, in both games, its only accomplished through fan-made plugins, but I'd think that it would only be more efficient if it were implemented as part of the engine by default.