For anyone coming away from an Arch based distribution and if you used it because of the package availability, Ubuntu MATE edition is a good alternative. In addition to a high package availability for Ubuntu, you'll also find that tools like the Y PPA Manager make finding and installing AUR-like software discoveries a snap. While I would agree that the AUR is going to be far greater in release to repo availability, the PPA system is quite good once you have a tool that will search the repos for you.
To me, Ubuntu MATE edition is a tool for those who value their time and want to get things done. It offers solid support for my work, playing video games and cooperates nicely across a large range of tested computer hardware. As things with this desktop stand now, I'd recommend Ubuntu MATE edition over Ubuntu proper all day long. It's dead simple to use, lacks the Unity learning curve, and still offers the handy Ubuntu underpinnings as an after thought.
To be honest, I hadn't planned on being this impressed with Ubuntu Mate edition. But my needs have evolved to the point where Ubuntu's release cycle makes more sense for me. Using the MATE desktop was just the push I needed to get me back into the Ubuntu way of doing things.
Does this mean I won't consider using other Debian and Arch-based distributions? At this time, yes, however only because I want a unified set of tools from which to run my software from.
The problem is, when I use other distributions, I tend to go wide and use a variety of them. That’s cool for awhile, however, in the long term it requires more care in maintaining those installations than I wish to spend. For me, Ubuntu MATE edition is just where I need to be right now.