I've been playing this game on and off since it's launch and it has gotten better from those days. My perspective is from one who only plays PvE(Player vs Environment) content. I'd recommend you try this game if;
1) you are not bored with the tradional WoW type MMO (hotbar combat)
2) you are Star Trek fan
3) you like to play doll with your character(s) (the character customization in this game is awesome)
4) you can live with bugs popping up (The new VP promises that bugs will be fix fast but only time will tell)
5) you can resist(or don't mind gambling) since there are lock boxes in the game which gives out a top prize of ships(basically classes in the game), etc BUT you can get all these things in game if you have enough in game assets to dabble in the exchange(auction house)
6) you don't mind the usual MMO grindfests which can get repetitive to farm better gear, etc
7) you are not a hardcore gamer
8) your internet connection to the servers is not crap
The gameplay itself is nothing to write home about and the main reason I'm still playing it is because it's the only Trek MMO out there. The game panders mostly to the casual crowd.
Contrary to some, the game in my opinion is not Pay to Win. You can have access to all the ships and gear if you grind enough currency to exchange for these items which other players put up in the auction house. Using real money is just a shortcut in the game.
Also this game features player created missions, some of which, are much better than the official ones. Don't forget to give some a try if you decide to try this game out.
In my opinion, Free to Play means demo and Star Trek Online's demo is surprisingly good in the sense that it's not restrictive like in some other MMOs. If your ISP does not suck and you can wait to download a 10GB or so game, give it a try and see if it's up your alley. Live long and prosper. \V/.