You may want to check an article in a prior issue of California Kayaker Magazine that talks about kayaking and small living places. It talks about inflatables and their limitations. Issue #9. Read for free at http://www.calpaddlermag.com/magazine.html
In general, inflatables are slow. There are inflatables that can put up with amazing conditions - the ones for white water. You wouldn't want to use on flat water. There are ones for flat water that can do decently (not as affected by wind and not as slow), but in general these are not the $400 ones you talk about. And the more expensive ones have more chambers and better materials, reducing the chances of troubles should a chamber get punctured.
Those $400 ones are considered by most as over-sized pool toys, so should be used in calm conditions on smaller bodies of water.
Keep in mind - inflatables are considered boats, so along with the kayak and paddles you are required to have PFDs.
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