I have the Curve, DH has the Storm. We love our Blackberries. I have mine set so that my main personal email comes to it. I love having the web browser. I mostly use the calendar- I can make appointments and schedule parties and whatnot and "invite" DH so that we both know what our plans are on any given day.
I also LOVE Blackberry Messenger- it is IM for only Blackberries. anyone with a blackberry email address can set it up, and you can message back and forth as much as you want. Because it is messenger, not text, it doesn't count towards your text allowance (if you choose to have one). Also, to help keep your text costs down, people who would normally text you can send their text to your email (enter your email address instead of phone number), so you get it free! I have told all of my family to send things through email instead of through text.
We also downloaded an application called Google Latitude that uses your phone's GPS to show your location on a map. If you want to see someone else, they have to approve it, and of course there are a lot of privacy things you have to agree to. I really like it because I can see how far DH is on his commute (he works about 40 minutes away). The one complaint about the application is that you cannot zoom in and see the exact location, so it is not great if you are lost and trying to get directions from someone else. But, the application does come with regular Google Maps, so you get directions and see your progress.
DH does not love his Storm. He has had multiple problems with the software freezing, causing him to miss calls (he can see that there is a call, but cannot answer it). Also, recently his battery has not been holding a charge. His web browser is better than the curve- pages load normally, but they are tiny. I did not love the click part of the touch screen, but I am sure that is something you could get used to.