Well, FWIW, I signed up for TGM last year just about a week before leaving on our trip, but was unable to get much of anything out of it due to some kind of problem the site was having at that particular point in time -- it'd take 5-10 minutes to load a single page, so it was practically impossible for me to navigate through enough to read any reasonable amount of the (admittedly VERY VERY copious) information there. I asked for a refund, and though I was somewhat annoyed by his emailed response (basically he said that yes, they had had technical problems, but he thought I still should have been able to get enough out of it to make it worthwhile), he did refund my money promptly.
So, this year, I pondered long and hard whether to sign up and give it another try. I finally did a few days ago, after deciding that this time I'd not ask for a refund even if it wasn't useful to me, because it didn't seem right to ask for a refund twice. Well, I've only been on the site a few days, and please note that I haven't been to Disney yet using his advice to see just how well it works in practice, but I'm already thinking it'll be worth the $19 it costs with the DIS discount. His best-days advice is far more detailed than I've been able to find elsewhere, and he really explains *why* he recommends what he recommends, which is great because it enables you to adjust the suggestions as necessary to suit your individual group's needs. The articles are very helpful, and I've found a lot of helpful information already. There are forums for discussion, too, and though the boards seem to be a lot slower than we have here, the people are very friendly and helpful.
Yes, it's definitely NOT automated -- expect to put quite a bit of time into reading through everything and following the step-by-step planning advice! -- and yes, there's an insane amount of information there, and navigation isn't as intuitively obvious as I'd like it to be. I would still recommend it, though. And as I found out last year, he'll definitely give you a refund if you request it, even if he doesn't agree with your reasoning
With a year and a half to go yet, you'll have PLENTY of time to browse, and like I said, there's a lot there that I haven't seen elsewhere. I don't think you can go wrong giving it a try.