I play occasionally. It's fun and enjoyable. And you don't need to raid endlessly to have a capable character. I recommend the Justice Server. I'm more partial to the Villain side, but they've learned quite a bit from CoV, and Heroes is now a lot more fun to play than it was.
If you do play, and want to listen to some tunes, goto http://justiceradio.net/ (the main reason why I recommend Justice server) and join the Justice Radio global channel. They often have good music, events, and helpful people. It's like a guild, but without the commitment, plus a soundtrack.
As for the download, the initial download is tiny; it's essentially just the updater. Run the file and it'll set up the folders and setup the game.