When you are typing known commands into the window, and the window pops up with a list of potential commands (aka intellisense), you should be able to press tab and have it auto-complete with the first item in that popup list (or have it intelligently guess which command you are likely to be using).
This is how it works with something like Visual Studio's intellisense. With the current Python window, pressing tab when you have partially typed a command like "arcpy.Sear" just indents the cursor, while I would expect it to complete the writing for me. Yes, I realize you can arrow down to the one you are looking for, but it would be nice if it started selecting the items as you narrow down to the tool you are looking for.
Even better would be intelligent selecting based on how popular or obscure a tool is. The geoprocessing tool search functionality seems to already do this intelligent guessing. It seems like the intellisense in the Python window could work a bit more like this search feature, while still highlighting the most likely candidate based on how specific you get with the command spelling.