If you are on a PC, there is no need to use Outlook or another mail client to check Gmail. Log onto the Gmail through a web-browser and there it is, and if secirity is a concern log in using https://.
On the portable devices, there is Google Mobile, and the GMail App. All of which are constantly updated, patched and improved. So again, why would you want to map GMail to your mobile device's inbox?
I only use Outlook at work because I have to, and that too I have made as GMail'esk as possible with folding conversations, smaller fonts and the like, but still, it can only go so far.
Just yesterday, I showed a colleague how to view by conversation in Outlook, and he loved it. For a non-Gmail user, this might take some getting used to, but once you view it in that style, you're hooked. It's simpley convinent to only see one mail at a time.
On the mobile apps side, I've used the GMail App as well and loved it. The only reason I had to stop is because the data plans in Canada are ridiculously expensive.
I know it's cool that GMail added another technology to it's arsenal to take another step over Yahoo and Hotmail, but what's the point really? Or am I missing something?
To top things off... Google has created a video that show you how to configure the IMAP functionality on the IPhone... How about showing us the same video on a GPhone... That is something I am truly waiting for.