I Have an SVI, STI, and a Atlas Nemesis in the making.;..SVI fit and finish is by far superior to the STI, have not had any issues with either pistol.
When i first received the SVI I called them on a regular basis for the first few weeks with lots of questions, Casey, Brandon and the girls that answer the phones have been not but cordial, attentive and have always answered my questions and have always returned my calls when they where not available. and by the way I bought the SVI from a 3rd party.
Never had to speak with STI with any gun related issues so I really can not comment on there CS.
Spoke with Adam at Atlas several times before I decided to pull the Trigger on the Nemesis he always took the time to answer all of my questions. Decided on an Atlas from all of the feedback on Enos, have never handled one so I am pretty stoke about getting on my hands on it and giving my own 2 cents about the build quality.