Hmmmmm. So, before I start it's worth noting that Magic Trackpad is a 10.6 only thing. If you're still running 10.5 (on, say, a very many thousands of dollars quad core G5) then can't have. Not for you. Also, and unlike many Apple peripherals, there is not even the claim of PC compatibility. It is "stock" bluetooth, however so I imagine some level of interoperability would be a goer - but probably not much. It did give the impression that compatibility issues may be a problem even when staying in the part of the garden that Steve says you can play in ... the included instructions say to use "setup bluetooth trackpad" in the bottom right corner of the "trackpad" part of system preferences. It wasn't there so I paired it anyway then did a software update and Lo and Behold! Someone has decided they want new software. An install and reboot later and everything is working as planned.
The system preferences pane for trackpad is now replaced by a very groovy setup pane including a tiny little video tutorial for each of the gestures. Nice. Sadly there is no detection of actually what kind of keyboard you are using so my initial experiments with screen zooming failed because I was pressing the button shown in the video - control on whatever keyboard they filmed it with, option on mine. Fail.
Then good things start to happen. If you forget you're playing with a new toy and start just using it like a big laptop trackpad then it just magically works. I tend to rest my thumb on the gigantic button on my MacBook Pro (on the rare occasion that I use the trackpad) and this works just fine on the magic trackpad. However, and for presumably the same reason, it can prove tricky to use your thumb as part of a zoom or rotate gesture.
Speaking of which, the zoom in Safari is really granular and gives the impression it doesn't work until ... it does. iPhoto suffers a little of the same, although preview seems to suffer less - particularly with rotation that it does reasonably well and almost entirely without purpose.
Seeing as how I'm supposed to be an Apple fanboy I suppose I had better say some nice things about it. Well, for a start the fact that you can click and drag without using a thumb means that MixTape is surprisingly usable. Perhaps this means that it's usable on all MacBooks with the single piece trackpad (all the unibody ones plus a few macbooks). The inertial scrolling is very cool although I find the "friction" on the inertia to be a little high for my liking and not configurable. Two fingers to context click is awesome although it would take practice to get used to it - likewise the four fingered swipe down to engage exposé or swipe up to hide all windows (an action like pushing all the stuff aside) could get very addictive. I'm just saying that because I'm addicted to middle mouse button as exposé through.
Is it worth it? I suppose if you really like trackpads it would be. I mostly have it so I can get MixTape to support pinch zoom movements (a user request). To be quite frank it's already starting to drive me up the wall so I don't see it getting far past that. It might be just *killer* for HTPC crowd - it would certainly be a lot easier to use from the couch that a mouse is, but then I have a playstation for that and it's even easier still.
Conclusion: loads better than a 'previous generation' trackpad. Play with one in the shop before you buy it. You might like it, or you might not.
Edit: Magic Mouse, on the other hand, is pretty much perfect.
Previous next big things include development of the capture and intermediate compression technology in iShowU-HD; design and implementation of a small advertising network; the refinancing, technical direction, and a lot of the donkey work for Virtual Katy; technical direction, project management and (again) donkey work for VoiceQ; creating code and intellectual property around load balancing that was acquired by Allied Telesis; and the research and an implementation of the h.264 video compression protocol.