Behind the curve here, but I only got my 360 at Christmas and I have it on rental. Incredibly fun, and while I usually do poorly at stealth at least being the Goddamn Batman I can grapplehook out of whatever insane situation I've got myself into. The dectective stuff wasn't too tedious for me, and actually I would use D-Mode in fights sometimes just because it looked all shiny and stuff.
I beat it on Easy (yeah, yeah, I know) and the boss fights could be a bit more, I did like the general feel of it and the atmosphere was splendid. I think I'll try to run through it on Normal before I have to return it in a few days.