Exactly same as ppc, I have used it in a shared environment so can't really tell much about its resource usage.
One thing compared to Plesk for example is easier and more obvious navigation, I guess some of that has to do with using the end user (less menus/options) version of directadmin but I have looked at the admin/reseller demos and to me it still looks a bit more intuitive.
It's been over a year since I tried it last, but the biggest problem I had with DirectAdmin was the way it littered the filesystem with symlinks, adding multiple (and completely unnecessary) layers of indirection to everything and making CGI environment variables like SCRIPT_FILENAME and DOCUMENT_ROOT inaccurate and unusable in many situations.
I hate everything about the way cPanel looks and functions, but the directory structures it creates at least make sense, and that's what matters most when I have to go tweak something the UI either broke or doesn't support.
I've used cPanel for about the last 10 years and just switched over to DA. The biggest complaint about cPanel is the server resources it requires. With the new version 11 out, you pretty much need a minimum of 512mbs ram. Currently I'm running 110mbs on my DA VPS. It also feels faster too.
How hard is it to switch to DirectAdmin from cPanel? I've tried their demos at the site and see some things missing that I use in cPanel, such as latest visitors, hotlink protection, etc.
Please keep in mind I have no clue about managing a vps, that's why I chose Knownhost (the absolute best). I set up my four domains and then treat it like an enhanced shared server, logging into the individual cPanels to do stuff.
I wouldn't miss it at the server admin level (since there's too much there anyway), but would at the user level.