The thing is, if someone tells you WinForms is obsolete, they are probably talking BS. Microsoft has never released a plan to cut support for WinForms. It will be supported in .NET 4.0, and for the forseeable future.
MS are good at keeping old/obsolete stuff working for a very long time, to their credit. I just wish they'd design and write a good UI framework and then stick with it for more than a few years at a time.
If WPF is finally that framework then great, but coming from a C++ background where we've had one neglected UI framework after another (and fairly limited design tools, code libraries and widgets), then seeing WinForms go the same way, and now reading various
complaints* about WPF, I find it hard to get enthusiastic. All those C++ frameworks still work but they're also all still more or less dead (though MFC, the one which probably deserved to die the most, did get a surprise set of updates recently).
(*Other people's complaints. I haven't used WPF yet myself.)