> Ctrl+backspace to delete the previous word in Windows always catches me out, since it works some of the time, but other times is just inserts a control character which I then also have to delete...

This is the single thing that prevents me from using Windows.

I dual boot with Windows on my iMac and I love the general appearance of Windows 7, much more than OS X. I feel like I can just get stuff done.

But then I try to work, and things just fail... A lack of common UI controls (Cocoa, OS X's killer feature) drives me insane when ctrl+a won't work, or a text field won't spell check for me, or I can't right click a word and get the definition of the word.

I find this is my problem with the iPhone as well. I got the iPhone 4 and 4S when they first came out as they are my best option out there, but I hate them so much. Other platforms are doing much more interesting things, such as Windows Phone 7's fresh interface, or the power of Android. However, all of these platforms lack the high level of polish and vibrant ecosystems the iPhone has.