Now we have smartphone and tablet coming to the market, which have moved PC to include Non Windows running systems, including Macs. However excludes light weight systems such as tables.
Now Tablets are getting more powerful so they may be adding the PC list.
I agree with you that a desktop, laptop, or tablet computer running Windows (for x86 or x86-64), Mac OS X, GNU/Linux, or Android is a personal computer. An iPad not so much because the "person" who owns an iPad lacks control of what "computing" is done on it without buying an additional Mac and paying a substantial annual fee. (I say "additional" because the majority of PCs in use aren't Macs.) Out of the box, the owner is forced to delegate this control to Apple.
The biggest distinction in practice between Android and the desktop operating systems is that Android's window management policy offers no standard way to split the screen into areas for different applications. But I'll admit that's not essential to the definition of personal computer because it also applied to most 8-bit personal computers, Macs pre-MultiFinder, and IBM-compatible PCs pre-Windows.