So far, so good. I barely looked at it (I hate reading things like this on the computer--I'll have to get it to work and print it out on the color laser).
It looks like a good purchase so far. I knew going into it that there would be no rules in it, but I'll admit, I do prefer supplements with rules in them (and I prefer CT rules....I haven't purchased in T20 or GT items yet that don't have CT rules in them).
I've been re-reading MT's Starship Operator's Manual lately, and it got me in the mood.
From just a casual glance, I think I'm going to consider Grand Fleet as a simple expansion to Book 5.
All-in-all, so far, I'd say it was worth the bucks.