Every time I use a tiling WM I think to myself "This would be incredible if I only used terminals and minimalist X apps (like xclock)". But the problem is web browsers feel extremely out of place in a tiling WM and I need web browsers so...
Perhaps it's just a cosmetic issue? For example, if you're using Chrome, you have to configure it to use system borders--otherwise it just looks wrong. I also set my Firefox up to be much more minimalistic, which looks much better with a tiling WM.
In practice, it looks like this:
Firefox: http://jelv.is/xmonad-ff.png Chrome: http://jelv.is/xmonad-chrome.png Tiled: http://jelv.is/xmonad-tiled.png
The only real problem I've had is that form widgets are rather ugly. I think this should be easy enough to change, I just haven't gotten around to it yet.
If there is a complaint about tiling window managers it's that applications like Inkscape or Gimp which have tons of floating windows tend to not render well. Though most WMs have solutions to this.
Granted I don't use the hyper complex layout you see in some screenshots around the web (Actually I don't know if someone really use those or if it's just for show)
I mainly split my screens into two or three parts. Using a tilling WM for this use case is perfect because I don't have to spend time resizing and moving my windows to take half the screen each time.