When I downloaded the version on Xbox, two things hit me, one it was unbelievably smooth, there was no lag whatsoever, and also the graphics were in a different league compared to the capabilities of my Mac. Obviously this will be different for everybody, if you have a top spec Mac, or any computer with a superior processor and graphics card, then the graphics will not be as different. Also the version on Xbox has some differences to the computer version. Firstly the map on the game is only limited to 1024x1024 blocks, as apposed to the computer version where the computer version has a map which is unlimited. The crafting is also different on the Xbox version, when you have the items necessary to make another item, you do not need to place them into a specific area on the crafting table like you have to in the computer version. Minecraft 360 is several versions behind the current 1.2.5. update on the computer, although 4J studios have said that in due time they will release updates for the Xbox so that it will have all of the features that the most up to date version on the computer has such as clay (which is currently not available on the Xbox version).
Minecraft is extremely popular, within the first week of its release on Xbox, 1 million people downloaded it, and on the first day there were reportedly 400,000 users playing it. I think that Minecraft, whatever platform you play it on, is a fantastic game, there is only one fault that I have found with the Xbox 360 version, and that is eventually, you will come across a world hole, this is where the path in front of you is a sheer drop when it shouldn't be there. If you just stand there it will eventually load, but I would imagine that the next update will remove this problem. Overall I think that it is a fantastic game, and in my opinion it is better on the Xbox for several reasons. The ease of using an actual controller, the fact that you can play with 8 people via Xbox live, the graphics, and also the endless fun that you can have on any platform.