I was thinking of the Blackjack as well. However having been a Palm User for a very long time and having tried Windows Mobile PDA's in the past I decided to stick with something that works, and works well (Palm OS). I love the form factor of the Blackjack, however I did have an issue with the way the number keys were placed. That was the only PDA/Phone I saw that had the numbers separated like that and not sure I could get used to that as much.
If I knew for certain that the Windows software was stable enough and that sync program that Windows uses didn't slow my PC down so much since it is always syncing as long as the PDA is docked I may have opted to go for that instead.
Also, look at the programs other than the basics that use on your 650. Those are programs that you will likely have to find replacements for and purchase new versions of that work with Windows Mobile. I mainly use Agendus Premium, DayNotez, The Splash Wallet Suite (Money, ID, Photo, Shopping) and Teal Auto, and I have not found anything yet that works as well as Documents to Go. DTG is even better than the lite versions of Word Excel and Powerpoint that are built into the Windows Mobile.
Just my thoughts, your mileage may vary
