I spent most of my early 20s pounding a 10-key adding machine. (Yes, adding machine, not calculator.) As a result, I developed wrist problems that plague me still. Finding a keyboard/mouse combination that doesn't cause pain has been a challenge over the years. Until Apple released the current low-profile style keyboard and the Magic Mouse, my standard procedure was to switch out mice/trackballs every week or so. Once I started using a Magic Mouse, that stopped. It caused zero pain. I love it.
Now, with the release of OS X 10.7 (Lion), while I still love the Magic Mouse, it can't handle all of the new multitouch gestures that can be used for navigating. Time for Magic Trackpad. I have a new love! After just a few hours of working with (and adjusting to) the Magic Trackpad, the mouse was turned off. And it hasn't been turned on again. I've used the Trackpad exclusively for a full week now, and I'm hooked on it.
I'm slowly but surely adjusting to the 2-, 3- and 4-finger swipes. On the rare occasions that I can't manage something that normally calls for a mouse-click, buttons are embedded in the feet on the front edge, so it just take a light press. While I haven't tested it, I understand that under Snow Leopard the feet can actually be assigned to right- and left-click. Sorry, not going back to Snow Leopard to test it out. Lion is definitely growing on me. I'm using it full time on both of my Macs.
One undocumented goodie that I found by accident concerns one of my favorite utilities, MenuCalendarClock. MCC puts a little calendar page with the date in the upper right part of the Finder menu bar. Tapping on it drops down a monthly calendar, and below that all of my iCal entries for the following week. I use it on a daily basis. I discovered by accident that a double-tap with 3 fingers anywhere will drop it down or put it away, even if I'm doing something in full-screen mode. Neat. For those using the Entourage calendar instead of iCal, there's a version for you, too.
I have no idea, yet, about battery life with the Magic Trackpad, but if I can get by with changing rechargeables every couple of weeks, I'll be happy. It's a great addition to my iMac. The Magic Mouse? It takes advantage of more multitouch gestures than the trackpad on my 2008 MacBook, so I have a feeling that it will end up in my laptop bag.