In all fairness, I've tried to complain less lately and play more. Really, the bugs that are mentioned aren't game breaking. The current balance is a little gamebreaking, but this is only if someone exploits it to the max, and tbh, most players don't. The exception here might be Illuminator spammers, while they are a pain in the ass, they probably are the only thing in the game that's left that makes me pull my hair out.
It's a worthwhile investment, however if I were you I would be watching for two things:
1. What Stardock reveals about Diplomacy. It looks like they will be adding a significant change to the game, and at the same time fixing balance issues.
2. What the community thinks of these changes. If you see the common posters on these forums (Cykur, Annatar, Eadtaes, Myself, etc.) Getting livid about the changes that are coming, then I'd say don't bother. I really don't think that's going to happen though.
My point. Let the feedback about diplomacy make the decision for you. Smart money says you'll end up buying the game and loving it anyway.