For me, the essentials are the Core Rules, APG and the Bestiary. I got by for a while without the latter - having been a 3.5 GM for a long time and having the Monster Manual, supplemented by the SRD. However, having the Bestiary itself proved really useful in-game.
I own UM which in my view...
Good strategy to aim at Hero Lab. I wouldn't worry about PCGen too much - it's functionality is fine and it's free...but assuming you can get each screen in Trailblazer to load within, say, 2 hours of the previous one, you'll have PCGen beat. (OK I'm exaggerating and PCGen is better on my main...
Good stuff. I read your blog post on the 7 reasons to create a character generator. Although I'd argue that - since several other generators already exist - six of your reasons are reasons to have one, not to create another. That said, the 7th reason is the best of all for creating one.
Can...