After checking out your latest version and getting exclusive locking up and running...it seems to work as a basic step 1, but files that are exclusively locked by another need to be visible in the client. It's quite often that a single file is not going to be locked but rather a group of related files. There is no way to know that a file cannot be checked out until you actually perform the checkout. If you are cherry picking files to be checked out and the 16th file is locked and the task requires the set of files, then it's a pain to uncheckout the 15 files you just checked out... I would wager that it's quite common when beginning tasks to view the current availability of files before starting the task.

We're on it... in fact it is going to be the main core feature of the upcoming 4.1 release which is especially designed for gaming...