Greetings and Welcome to the Forum
I do the exact same thing you are asking about here. I have four different BB's and my wife has one. I like to change from one to another just because I like choices and I have'nt met a BB I didn't like yet......
I use the personal BIS service, the desktop manager, and Outlook 2003 on my laptop. From this one Outlook database (with 3,200 contacts) I sync with anyone of the four BB's I own, as well as her BB. I have a very dynamic busy schedule so therefore I sync at least twice a day, plus once in the evening of hers so that she and I are ready the next morning.
The sync process is amazing, about 10 seconds and I'm ready to go. Completely reliable, stable and super fast. The BlackBerry is the first PDA or Smartphone all of all the platforms I've had that sync's so flawlessly.
I did have problems initially with the older version of desktop manager that came in the box with the BlackBerry's. Then I learned from someone else on this forum the solution was to run the newer desktop manager 18.104.22.168 (July 26, 2006) or later. So I went to the RIM website and downloaded this version (free) and it works perfectly everytime.
Once in a great while (1 out of 200 syncs) it will not sync correctly probably because my database is so large. However this only occurs when I connect a BB that I have not used for awhile. And the solution is super easy and fast:
With the BB plugged in via USB cable, open the desktop manager, double click on the backup and restore icon. Click on Advanced
On the right side window it will be labeled Device Databases. The first entry is address book, click on this to highlight it. Then click on the button below to "Clear" it. Repeat this same procedure of selecting the calendar, and tasks. Once those three fields are clear your BB will be empty of data. The click "Close" to get back to the desktop main window. From that window double click on Synchronize and it will restore all that data you just cleared. As well as anything new in the computer.
I do this once a week even if I'm not having problems, just becuase my database is huge, this process is easy to do, and then I know everything is "Fresh" if you will. Also it's very important for you to know that I have been doing this for over six months with no problems whatsoever.
If you have any further questions, please ask. I'm sure you will be very happy with two BB's sync'd to one computer.