8.1 is a good step up and the next one should take it up another notch to. We'll have to wait and see if they can stick to this new release cycle though but I believe they can, no reason 8.2 should take longer than a year if most of the updates to it are UI tweaks. 8.1 added a load of new APIs and I think they'll wait a bit before adding a bunch more so developers can keep up.
I expect a boost in the quality of metro apps on 8.1 because of the new APIs though, look at the updated mail app that comes with 8.1 for example. I see that as a huge jump in functionality specifically because of all the under the hood WinRT updates 8.1 brings.