I tried the demo on 360 and I LOVED it, I'm just not sold on wether it is worth $50 - 60 depending on where I buy. How long is the game? And how is the replay value? 
 
EDIT: Oh and I meant to say sorry if there is a topic about this already, I didn't see one.

Probably worth it. I've just been keeping it from blockbuster for way past its due date. Probably put around 8 hours into it.... only at 50%. I do a fair amount of collecting and stuff, though. I can't speak to the replay value of the game, but there is a challenge mode that's probably fun, and the main campaign itself is surprisingly lengthy. Rarely stale, too. I keep coming back to it... continues to impress me

Definitely worth it. The game can be up to 25 hours long, maybe more, for a single playthrough and with the extra challenge rooms, you will want to stick around and play more of it. Second playthroughs are also tempting.

Cool thanks for the info, the single player sounds like a good length, especially compared to most games nowadays. I wasn't sure if the Xbox version got the challenge rooms as well or if those were part of the joker promo on PS3. Well if the Xbox has the challenge rooms as well I'm definitly buying. I couldn't care less about playing as the joker, I watched vids on youtube and he actually looked pretty lame compared to Bats.

i would say no. I borrowed it from a friend and that was more than enough for me.

I kind of agree.  I rented it and beat it and don't really feel the need to replay right away.  Maybe when it drops to 30 dollars I'll consider picking it up to pop it in again. 

OK, here's a new one... should I get Red Faction Guerilla or Batman?

Can't speak to Red Faction, but I know I'm positively enjoying Batman.

That said, I don't know if it has a lot of replay value. Obviously, there's an achievement for completing the game on the hardest difficulty. But I've put nearly a weekend's effort into it and have nearly completed everything the game has to offer.  
  
The campaign is very fun. The challenge rooms are very enjoyable. At the end of the day, though, I can't promise you'll find sixty dollars worth of content in this package.

Honestly, yes. Between Red Faction and Batman though, I'd go with Red Faction. More replay value (i.e. mutliplayer), but I'm going to definitely buy Arkham Asylum once I get the money. GameFlying it isn't enough.

Yes. Definitly worth it.
 
I've put about 30h into it. For 100% completion and 1000/1000 achievement points.
 
Best singleplayer experience I had so far this year.

Worth every penny, then again I bought it for $38 because in canada futureshop wanted to match the price of wallmart. Still for full price the gameplay is really excellent and there is replay value, I am going though it again right after I finished it and trying to get all the joker's riddles. There is a challenge mode for more replay value, it's definetely worth buying, I have no regrets, except that it's not the pc version which is sharper.
 
About red faction, no idea.

It would be a yes and no question. I personally think the game was worth the $60.00 I paid for it, because I love Batman related things. But the story felt way short, even while getting all the Riddler challenges completed in the same play-through. I don't have much interest in replaying it right now, but the challenge rooms are just that, challenging and they can keep you occupied (and frustrated) for a good deal of time I'd imagine.

" Yes. Definitly worth it. I've put about 30h into it. For 100% completion and 1000/1000 achievement points.  Best singleplayer experience I had so for this year. "

Yes

yes.... what the people have said already and that theres also free dlc coming on the 17th and the 24th

I wasn't sure whether to buy it or rent it but i stuck with my pre-order. So happy I did as even though i've completed the story i just keep coming back again and again.