I think it's most definitely worth getting--and I, for one, think the freeform galactic conquests give the SP side of things a high replayability factor if you're the kind of gamer who spreads out his gaming time instead of packing in a twelve-hour gaming bloc immediately after your purchase. Of course you'll run right through the game if you do that, but that's often true of games these days!
I find myself coming up against real strategic decisions often, especially on the galactic map. Of course you'll find yourself building a lot of mines early on, but it doesn't have the same peon-rushing feel of other RTS games. The galactic map/tactical battle integration is a really neat dynamic. The only lackluster thing strategy-wise is the game AI; you'll find yourself scrambling in the early stages of a conquest game on hard difficulty, but as you amass credits and forces, you will basically have a huge garrison fleet over every front-line planet. In the early stages, though, you may have to decide whether your forces should sacrifice that planet in favor of this one, whether taking the next world will spread you too thinly, or whether taking another world could give you tighter control of hyperspace lanes. I find it very satisfying from a strategic point of view, but the AI seems to slack off after the balance of technology and power shifts towards the player. Online, of course, you won't have this problem, and it's likely that an expansion or even community-generated mods will help things in that department. (Unfortunately, without the mod tools out yet, mods are limited to basically changing unit stats and all the stuff out there are just "OMFG the ATAT isn't totally unbeatable WTF make its health 100000000 and damage 999999" mods.)