I would say 24" is great upto 1920x1080 or 1920x1200 (if you can find one)
But anything above that size wise you want to start increasing the resolution otherwise the dotpitch gets to the point of 'too big' and you start to notice pixels.
However, pushing 3d to the 2560x1440 resolution will require 1) Some graphics horsepower and grunt and 2) probably a reduction in image quality.
As much as 3D is touted as 'yeay' tbh I've found it fairly lackluster in testing. I've not invested in it for gaming as it just doesn't really feel like it's right yet. Fixed Point of view means it doesn't really feel like you're 'there' and if there's no headtracking the illusion is broken really.
I've not got a lot of experience with it YET, but all examples i've seen so far, without headtracking of some kind it just doesn't quite 'snap' correctly.
There's some research into using a Wii remote to create a 3D effect using headtracking that works with a camera, (because it's not got 2 lenses) something like this COMBINED with 3d, would really make it work. But just having it expand out the screen just doesn't really work for me. It needs interaction...
If this is in place in the current 3d tech I'll gladly back off and shurrup lol. (any one wanna chime in on that one?)
I'm not trying to talk you out of it, not at all, but I was seriously considering it and went with an IPS screen instead (a Dell one) and i'm happier with the better colours tbh
I just read that product you linked to and spotted this
"Gaming is in the details
The XL2420T demonstrates BenQ’s true belief that "gaming is in the details" It has been co-developed with Counter-Strike pro gaming legends to bring you a gaming monitor like no other – from the attentive designs to the exceptional functions. With the precision and speed you would expect from a high-performance gaming monitor, you can now have a vantage point over your opponents in all your game play."
So they spoke to Fatality, and made it have red bits... it MUST be pro!