The biggest missing feature of all: a roadmap
Committing to a product roadmap is always a tricky thing. You don't want to portray your future products as being so spectacular that someone would be a fool to buy now. But equally, you don't want people to be scared off from using your platform just because of uncertainty over what the future holds. There's a definite balancing act to perform, but so far, I think Microsoft has tended to lean too far towards "uncertainty over the future".
I like Windows Phone 7 a lot. It's eye-catching, and people seem genuinely impressed when they actually get their hands on it. I hope it has a bright future. But I recognize that it's got a lot of gaps. Gaps that need filling to put the operating system on the same terms as Android and iOS.
I'm sure these gaps will be filled, eventually. But I don't actually know at the moment. Someone buying a Windows Phone 7 device right now is taking a bit of a gamblethey're gambling that the missing or incomplete features are going to get added within a reasonable timeframe. If it turns out that we're going to have to wait 18-24 months for multitasking, say, I think a lot of early buyers are going to feel short-changed. After all, if you have to wait that long, you might as well sit out this generation of devices and stick with Android or iOS in the meantime.
Talking a little more about the future, telling us at the very least what kind of upgrade schedule we're going to see, and giving us a feel for the scope of the upgrades, would do a lot to improve opinions of the platform. It makes picking Windows Phone 7 less of a risk, and more of a certainty. The confidence that the platform will become an equal peer to iOS and Androidand soonis the most significant feature Microsoft can add.