Xmonad/awesome (haven't tried i3) are absolutely fantastic, however, in my experience, you need to spend some days tweaking configuration files in order to achieve a satisfying experience (especially if you want dual-screen support to work in a less... interesting way in Xmonad). From what parent was writing, this is exactly what s/he does not want to do.
Coming from Metacity, Xmonad's handling of dual screen is definitely different but I prefer it now.
Instead of treating both screens as an extended single desktop, each screen is on it's own desktop. This allows me to mix and match desktops at will (most common with documentation), or I love swapping the two screens with each other with this line in my xmonad.hs (https://gist.github.com/2657206):
In my experience i3 doesn't require any tweaking. It has really sane defaults about pretty much everything. If you do want to configure something, the configuration file is extremely simple and the documentation is really excellent.
The default behavior when using a dual screen setup is each screen having some of the workspaces.
Yeah, the only thing I have ever customized with Awesome is changing the default terminal to xterm. After that it just does exactly what I expect, and doesn't get in my way; I don't know what more I could ask for.