I have a Sig Fastback Carry and absolutely love it. It had a slight issue on its first range trip with the slide not locking back and erratic ejection, but I was able to fix that by replacing the factory mag release with a Wilson Combat mag release...solved both issues.
I love my Ultra Compact 2 Two Tone. It has been accurate and 100 percent reliable. Not one problem even with some cheap ammo. The trigger is short, sweet and breaks very consistent. I have 3 other Sigs and have no issues of any significance.