Spaces was the multi-desktop feature in Mac OS X Leopard that has now been rolled into Lion’s Mission Control, which also incorporates Dashboard and Expose. I have heard that Spaces wasn’t used by a lot of people. I used it extensively and loved the flexibility of it. I had Spaces set up as a grid of six: three on top and three on bottom. I had certain applications pinned to specific spaces. For example, space number four (bottom-left) always had Mail on the left display and iCal on the right display. Space two (top-middle) contained iTunes on the left and TweetDeck on the right. Some applications, like Safari, were left to open in whatever space I was looking at when they were launched. Then there were other applications, such as Skype, that I set to display in every space. Using the control and arrow keys, I was able to quickly move between spaces, each space being no more than two keystrokes away.
Mission Control isn’t as robust. I assume Apple decided to simplify Spaces in an effort to make it easier for more people to understand. All spaces are now in a single row, rather than a grid, so it takes longer to navigate between them. There are keyboard shortcuts to jump directly to them, as there were in Spaces; I just need to learn them. They didn’t retain the preferences for assigning applications to spaces, and there is no way to make an application present on every space. Mission Control allows me to move windows from one space to another, but unlike Spaces, I don’t have the freedom of dragging a window from any space; only those windows in the current space can be dragged. Furthermore, I can’t drag a window from one monitor to the other monitor in a different space. I must first drag the window to the other monitor in the current space, and then drag it from the current space to another space, requiring two actions instead of one. This all makes the rearrangement of applications and windows a bit tedious, and I find that I’m doing it more often, now that I can’t specify where I want applications to open.
Hopefully, Apple will return some of Space’s functionality in future updates.
Correction: See post for 8/8/11, Desktop Underpinnings