The giant icons are actually not that easy to hit with a cursor (probably easier than small icons but, b/c of their size, they give the mistaken impression of being easy to hit while not having the advantage of an infinite edge to rest against). That aside, searching for icons in that way is not very fast (when they add paging that will help a bit, but still doesn't fix the essential problem). Spatial memory is only good for a relatively small number of frequently used items. It simply doesn't work well when you have many, many things installed. So, ignoring typing, you need a way to quickly filter the items down to a smaller number. Traditionally we've used categories to do this but the GS designers are planning on getting rid of those in 3.8 (last I heard). Considering the way categories have been exposed (way off to the right with a list that is fairly difficult to interact with and parse) I can understand why they want a change but getting rid of them all together is going to make the problem worse.
The hot corner needs to go away. I really like using it. I LOVE using it. It's one of the best things GS has done (aside from incorporating some web tech), but it simply doesn't work with multimonitor setups, especially when you consider eyefinity type setups. Also, xcapture isn't a solution. It's a bandaid on a gangrenous apendage.
The virtual desktops need to go away. I never use them. My GF (a UX person) started out using them and gradually stopped doing so. She tells me they didn't offer task isolation b/c she uses maximized windows (she mostly uses her 12.5" laptop). When she uses multimonitors she would put multiple items on one screen but on her main screen she works with a maximized window. When she changes windows she uses alt-tab which will ignore workspaces and show you all your applications. So, in short, if you use maximized windows, which seems to be the suggested usage for GS, the virtual desktops aren't very useful. As I've said in the past, a better model to use is ad hoc window groupings (Panorama) that you can name. It is a really natural way to interact with windows and has a low cognitive barrier AND allows you to see what is where easily in overview (alt-tab would be as efficient as ever). Additionally, these tasks need to be persistent. That is, if you shut down the computer with them running you can expect them to open up again in their task groups when you log back in. That is something that you can do, with some effort, in various other DEs, and it is a good idea. Things that you do often need to be as easy to do as possible, and applying no effort towards a task IS as easy as it gets.
Frankly, there is so much more, but this is enough for now.