Windows Mobile 6 and 6.5 weren't as stable as newer operating systems including iOS, Android and Windows Phone 7. That hasn't changed much even with a particular phone's revisions. That doesn't mean it will crash every 10 minutes but you should reboot the phone every few days to keep it running smoothly.
The benefits are as you listed: you get MS Office apps, more robust email clients than can handle most any type of email account (feature phones are often limited when it comes to email support). You also get syncing while there's usually none, or very weak syncing with feature phones.
You can generally sync quite a lot of Outlook data-- say 2,000 contacts, scads of appointments and notes. If you have 10,000 contacts, the phone's contacts app will probably crawl.
Be warned that if you're buying the TouchPro2 with a contract, they usually require a data plan.