1) It blocks part of the screen, and too often blocked things I wanted to see while typing.
2) It was not a reliable -replacement- for the command line. often times it would not display output information that the command line WOULD, that I needed. I'm sorry I can't give specific examples, it has been too long since I decided against it, and memory escapes me.
3) I am a command line junkie, and type all my commands instead of using buttons or menus. I don't use -any- buttons or -any- menus for commands, actually, with -extremely- exceptional circumstances. I do not need to -see- every command I am typing, either, so when the text pops up, it truly is simply "in the way". Being a command line junkie, I type a lot, so it's blocking my model and/or other text/dimensions often.
4) Whenever working in 3D, it has DRASTIC performance problems, possibly due to my video card, when the overlays/tooltips/command-entry is shown on screen during any visual style other than 2dWireframe, and comes to a horrible, snails pace, choppy lagtastic regen rate. It's like my screen will only refresh once every... estimating here... 2-3 solid seconds. It's terrible. Like I said though, very possibly due to my video card, nVidia GeForce 6800. I've noticed the same problem when other dynamic windows from other applications pop up over AutoCAD such as Firefox's alert telling me "downloads complete" scrolling out, and back in, to the windows task bar.