Honestly, If your mildly interested (or more) I see no reason to wait on purchasing unless it's due to financial considerations. Sure the game 6 months from now might be way better than 4 days from now, but that can be said about almost any game. Truth of the matter is Stardock did a real Beta which isn't common anymore. A lot of people raised issues/concerns because their expectation of the 'beta' would be similar to what other companies call a beta. For instance, I participated in both of Cryptic's Champions Online and Star Trek online Betas and the game they presented was pretty close to what you got on release date. These in truth are more stress tests (server load balancing etc) or simply a perk for pre-ordering.
Unlike Cryptic, Stardock really took advantage of the player base and beta testing process. They listened to many ideas, concerns or issues that confused players. So the version you'll see on Tuesday should be a pretty solid game, especially single player. So most of the concerns from Beta should be brushed aside.
I believe Brad has spent the past week or two solely on the AI for this game and if I recall, he made a comment to the effect of not being happy with the AI until it can beat stomp you on Normal difficulty. Again the AI 3-6 months from now will likely be different, but you should have an enjoyable experience at release.
Hope this helps and good luck with your decision.