I don't see any reason to run gitosis when there's gitolite, even for a single user. Either is definitely preferable to doing things manually, though.
Doing it manually for me just means (on the server):
mkdir project_name
cd project_name
git init --bare
I already have ssh keys set up from long back, so that's all I have to do really. Then I just add the remote repository on my local machine.
Setting up gitolite is dead simple - setting up a git server manually manually might be 'simple' compared to other tasks, but it's still unnecessary work. Creating new repos is as simple as changing the config file and pushing it - no need to do anything on the server at all.
I see absolutely no reason TO do it manually, and that's the decider.