I have to say that this is one of my favorite games for the Xbox. I bought it the week it came out for full price (and I never do that...), and I dont regret it. The strategic elements are pretty well done, and I generally found the interface to be solid. The only thing thats terrible about the game is the English voice acting, but you can switch to the original Korean should you choose.
Its just a blast. It combines action, RTS, and role playing (upgrading troops, weapons, etc) pretty flawlessly. Furthermore, the music just fits the game well, so the lack of custom soundtracks doesnt bother me.