Having the search charm work with the app is great, but who says that you can't include an additional search method as well?
I'm pretty sure the design guidelines actually call that out specifically as something you shouldn't do. Having a consistent way to handle search in all apps is one of those things that will almost certainly pay off in the long run, even if it takes a little getting used to in the beginning.
My experience so far has been hampered somewhat by video driver crashes making startup a bit of a hit and miss scenario, which all too often ends with Windows doing a self recovery. In fairness, using any ATi driver update other than the one which originally shipped with the laptop turned Windows 7 into a blue screen-fest too, so hopefully once I've downloaded that one I can get it installed and things running a bit more stably.