Welcome to MTR, IBD.
There is a LogMeIn app for iPhone available on the App Store, and I can confirm that it works well. I don't think there is a Windows Mobile application for LogMeIn per se, but accessing https://secure.logmein.com/pda from an ARM-based Windows Mobile device supposedly works well.
The iPhone can view Office documents, but apps for actually editing them are only just beginning to emerge. Windows Mobile devices do have several options in this area - besides the included Mobile versions of Word and Excel, there are alternatives like TextMaker available for purchase.
There are dozens of Windows Mobile phones out there, so I can't make any blanket statements about reception or voice quality. I'm happy with my iPhone in this and other aspects, but you could say I'm a little biased.