While I agree that WP7 is a GREAT OS and will be much improved after Mango, I have to respectfully disagree about it being "the most secure OS" and having Office. Coming from a BlackBerry environment, and not even having an Enterprise Server, I can tell you that BlackBerry is MUCH more secure. Little things like limiting the lock screen password to 4 digits is much less secure.
As far as it having Office, it at best has an ultra-stripped down Office compatible suite. Formulas in Excel can't be entered (although I've heard that improves in Mango) and it's a pain to move between multiple sheets in a spreadsheet. Even the crappy Docs to Go on my BlackBerry worked better.
All that said, I still prefer the WP7 OS and I truly believe that, in time, it will mature and improve in those areas. With Mango's release, I will be once again moving back to WP7.
And, just to keep this thread somewhat on topic, my wife just got her new HTC Trophy over the weekend and she likes it so far even though she doesn't have a Facebook account, or Twitter, or any other social networking accounts. I think they're a great plus for those who do have such accounts but not having them doesn't preclude the usefulness of WP7 in the least.