I own a Dell U2711 27" 2560*1440 IPS monitor and have a 23" 1920*1080 TN panel right next to it. Both are calibrated so colours are accurate, and there is no comparison between the two. Colours, blacks, everything is miles ahead on the IPS panel (my main screen). I did a lot of research before buying this monitor and backlight bleeding was only a real issue on a single Dell IPS monitor according to many reviews I read (might have been the 23" IPS possibly?).
Also I don't really know where you are coming from with the "true 8 bit colour" comment (please enlighten me if I am missing something). I dont find 8 bit colour all that impressive, all my images are stored as either RAW or TIFF files in the AdobeRGB colour space, and you can tell the difference especially in the greens on foliage if you drag the image so it is visible on both screens (10 bit AdobeRGB left vs 8 bit sRGB right).
Contrast ratio is largely a Con on the part of monitor manufacturers. Basically they just make the blackest and whitest pixels darker / brighter respectively and stick a "1 million : 1" contrast ratio sticker on it. Every pixel in between can be identical as they often just focus on the pure black pixel. I've also always hated "dynamic contrast" options on monitors.
On the subject of response times, I have never had a problem with the either screen. I was always the person that could not stand 60Hz CRT monitors and I could always tell if CRT screens were at 60 or 70Hz, but I have never had a problem with response times. I'm sure some more hardcore gamers will disagree with this though.
Basicalyl if image quality is your main concern (as it is mine) colours, contrast, viewing angle, you will never go back once you go IPS. If gaming performance is more important to you then you might be better served buyng a 120Hz monitor .