How long is inFamous?

Depends how you play. I'm guessing a complete run through ignoring all missions and Blast Shards would take around 8 hours to complete.

I'd say completing the game in only 8 hours ignoring everything but the story missions is damn near close to impossible, you'll need Blast Shards to increase your energy bar and you'll need to use Side Missions to Increase/Decrease your karma and gain experience. Your Karma and Exp points are important for buying upgrades and Karma is important because you'll need Maximum (good) or Minimum (evil) Karma to get the best powers.

Calculating all of this it could take around 15-20 hours from the start of the story to the end of the story depending on how good you are. And assuming you'll want to play through it again for the other Karma side (currently what I'm doing) it would take you probably an extra 10-15 hours (you should be much better on your second playthrough). This is excluding trophy completions and completing in game tasks such as, obtaining all Blast Shards and taking over enemy territory this could add several hours more to your game time.

This is definitely worth a try, I know some people who don't like it much, but I love it, and most people who have played like it also, it's definitely challenging (as long as you don't play on easy) and the gameplay is fun, especially when you get the more versatile powers. Story is definitely a positive, with interesting characters and bosses. The Karma choices sometimes seem a bit tedious (Kill or save) but most are pretty interesting.

Oh yes, and DO NOT judge the full game from the demo, the demo doesn't have a fraction of the stuff in game

Infamous Gameplay

Its fun and really cool. It is pretty long as you can finish both infamous or as a good guy so you can play through the game being good and then play being infamous. However once you beat both sides of it and get 100% on the trophies there is, really nothing else to do because there is no online multiplayer

inFAMOUS... AWESOME GAME! I finished it and it's fairly long. The storyline is really deep, the game play is really enjoyable, the karma system works great and overall it's a great game. i played the demo and then i HAD to get it because i was so addicted to the demo! i remember on a video or something it said that the side missions give to you 3 times as more play time as the storyline mission alone, not SURE though.

If you just went through the game (Like you just like went eh and skipped some of the side missions and etc...) probably it takes about 15- 17 hours straight.

But if you like played the whole thing then I might say about 32-34 hours or more (depends) straight.

I only played the demo and played it at my friend's house and it looks pretty cool.

It's looks like GTA 4, but you have super powers to it.

Story was really interesting

The only problem that I see on the game is that the characters movement is weird and their mouths in the game compared to the actors doesn't quite match.

There are other issues but not a big deal about it. You'll just get used to it.

Game looks really good overall, I want to buy it (If i can hopefully)

Edit: Also played the "Actual" game at my friend's house.

like the guy said above me it is really cool and fun i got it the same day it came out and i have not beaten the game yet but i tell you it is really fun it is probably like around 20 hours long just the main storyline and it could take you up to 50 hours getting everything else like getting all 350 shards, all dead uplinks and the side missions but after you do all that there is nothing else you can do unless you want to keep on playing the game for the storyline only.

I didn't play it however from what I know it has something like 30-35 hours of gameplay.