I have the mouse on the main surface, which is a bit annoying to have to reach up to

The desk rolls easily on most surfaces (carpet is a bit more difficult) and holds my 27" iMac with plenty of room to spare.

If you slide the keyboard over so it hangs off the shelf a bit, there is room for a mouse.

and you can see the monitor shake a little bit as you lean on the desk to type of move the mouse around

My monitor shakes a bit when I type fast, but it isn't stopping me from buying a new one