pfSense

Tested with:

2.2-BETA (i386) 
built on Mon Nov 24 02:45:36 CST 2014 
FreeBSD 10.1-RELEASE

I have enabled default gateway switching in Misc -> Advanced since 2.1. In my 2.1.5 setup it works fine, if WAN1 goes down, it switches to WAN2. If WAN1 comes back, it switches the default route back to WAN1 (Verified this by restoring my old 2.1.5 KVM).
With 2.2 this seems to have stopped working at some point in the betas. Bringing down WAN1 makes it switch to WAN2's default gateway. But it does never switch back when WAN1 comes back online. When I press Save/Apply on WAN1 I can force it to switch the default gateway back. But it won't do it on it's own anymore.
Another test to see what happens with WAN2 going down:
-switched off WAN1 router
-let it settle an switched WAN1 router back on
-the default route stays with WAN2 as noted above
-switched off WAN2 router
-let it settle
-the default gateway is not switched back to WAN1 as I would expect, it stays with WAN2.

The web GUI is really unresponsive during the test.

And my gateway cannot send mails anymore:

Nov 25 05:44:51 xxx.xxx.de php-fpm[14109]: /rc.dyndns.update: Could not send the message to xxx@xxx.de -- Error: could not connect to the host "smtp.1und1.de": ??