Due to a unwavering time constraint the developers were unable to actually finish the game. Thus, many popular video cards went completely untested, and features never put in, etc, in a mad rush to get it "acceptable" for release. I do believe that the graphics card is the biggest issue... but as for if the game is worth it, some people say it is, many say it is not. The controls do not work well with the PC version, it feels like a crappy port of the 360 version, even if the actual porting was the other way around. You're also unable to remap the keys to try and fix the horrendous controls.
As well, combat is kind of simplistic, but it's hella fun if you can get it to run smoothly.
I'd say that if you have a 360, get it for 360. It works fine on that system and the controls are good.
If you can get it to work fine on your PC, it should be alright so long as you get a 360 controller, I think I know a few people who said the game is just fine with the right controller.
As for the story itself and stuff... pretty epic. If it weren't for the technical issues, control issues, and some simplistic combat issues I'd put Legacy up there with Armada and Elite Force in terms of quality Trek gaming.