Elecraft T1 auto-ATU which works very well with the FT817, especially with the FT817 interface cable which automatically retunes the ATU when changing bands on the rig if the settings have previously been used. Just recently I started to have problems with this ATU when sometimes it simply refused to work. I contacted Elecraft for help and they replied to my email overnight, which was pretty good customer service. In the end it looks like the problem is just battery contact pressure: I managed to snap the plastic that ensures good pressure on the battery contacts and, by chance this evening, I found that pressing the battery hard brought the unit back to life. I may replace the 9v battery contacts with a snap connector.
On the subject of QRP auto-ATUs, has anyone experience of the LDG Z-817? This is a bit bigger than the diminutive T1 but in some ways is a better arrangement for home use. This has to be retuned every time bands are changed but the method of interfacing to the FT817 control (to change mode and power during tuning and then switching back automatically when done) is good. The memories also store previous tunes so retuning when changing bands takes just a second or two I believe. I also like the way the Z-817 sits on top of the FT817. The T1 is fine for portable use but I never quite know where to put it when used on the desk at home!
Now, of course, if the FT817 replacement ever happens (Dayton in a few weeks maybe?) we will expect to see an ATU inside the rig, as for the Elecraft KX3.