I've been using Garageband the last few years, with a bunch of extra virtual instruments, and it's served my purposes well. I've only been doing some scratch outlines for songs, the ocassional small scoring job, and the like. Now I'm gearing up to do more work, I'm working with a few different vocalists, writing with them, and have some slightly larger, though still small, scoring projects on the horizon. For the most part it will be a learning process on my part, so I don't need perfection at first. But I'd like to have access to good scoring/video tools, good recording environment for singer/songwriter stuff, and a big fat orchestra ready and waiting when it's time to do some of that kind of scoring.

I'm guessing that eventually I'll want to be using the full Logic Studio, and various virtual instrument plug-ins etc, but to get my feet wet (and since the economy sucks rocks) I was thinking of starting with Logic Express. I've seen various lists of what Studio has that is missing from Express, and it seems like I would't miss it much, if at all. (btw I'm wanting to stay all apple here, just for simplicity's sake. I'm doing that with web stuff etc, and it works great for me. I used Perfomer back in the day and love the interface, and wouldn't mind using Digital Performer at all, but as I say, I'm going all apple here...)

So my question is, for what I'm wanting to do, will Logic Express be fine do you think, or will the omissions drive me crazy and I'll want to have Logic Studio right away?

of course this is subjective, but i say pony up and buy the full version. you will eventually.
but trust your feelings. as you work, they'll be your foundation, more than any specific software platform. will you feel comfortable? capable? professional? you may know already what it is you really want/need. go with that.