I love the way the Gehn shard runs in a window for me.
The window is very stable, and it's real easy to leave and re-enter. I like very much that my cursor is never "locked" inside the window, but that I can click anywhere on my desktop without any extra moves or hot-keys. Re-entering responds to an "alt-Tab" with no trouble at all. Neither MO:ULa nor any of the other shards I've tried are nearly this easy to use.
Using this shard is a pleasure!
On my widescreen laptop, I'm running Uru in a 1024 X 768 window that gives me plenty of additional screen real estate to work with.
Alongside Uru, I have the Forum in Firefox, my screen capture utilities, PhotoShop, and Notepad easily clickable.
(I'm running x64 Vista in 12 Gigs of ram on a dual-core, with my Vista hacked "Trusted Installer-free" and only me in charge.)