I wanted to chime in. We've been having a great time flying all over California for the past couple months in our Viking 110 powered RV-12. So far, we have about 70hrs on the plane. No major squawks with the engine yet.
They have had a couple required updates (flywheel, etc.) that required some extra work (flywheel replacement, etc.), but really not all that difficult, and the SB's seems to be on par with and the Rotax and RV-12 in general.
I did get a chance to spend some time in an SLSA RV-12 with a Rotax, so in comparison to the Rotax, here are my observations...
1. The liquid cooled engine seems to be less finicky in the hot weather here in California.
2. It seems to start easier, and sounds a little better too.
3. It also seems to climb and cruise slightly better than the Rotax.
4. It was approx 20# heavier than the Rotax, so I did give up some useful load.
5. It definitely took longer to build with a custom panel and engine requiring more work and head-scratching, but for me as an engineer, that was part of the challenge (and fun). Maybe + 6 months.
6. It was also a choice to go with an engine that does not have the same level of experience in the air as say a Lycoming or Rotax, but I did wait until there were several builders with a couple hundred hours, and did my research before jumping in.
So far, I'm pleased with my choice to build the -12 with the Viking. I'll try to update again in a year or so after I put some more hours on the engine.