If you're a fan of Star Trek, put simply - you will LOVE this game: it is superb. Worth every penny and FUN FUN FUN :)
There are 2 parts to the game: ground exploration and space exploration. For both, your bridge crew determines what sorts of abilities you'll have and with each bridge crewmember and ship being highly customizable in both form & function? Everyone gets to have a unique experience while playing that's purely based on their personal preference. Into PVP? Ground and space options abound. Interested in a massively multiplayer invasion of a Klingon-occupied planet? Borg? Gorn? Romulans? You get the drift...
Advancement is great fun too. Why? As you get promoted, you get to choose a new ship - and this experience alone - is worth the price of admission.