Freedom Ventures, the STI distributor, is great to deal with.
Freedom Ventures keeps all STI parts in stock. Once, when I wasn't happy with a new pistol, I was told that it was my choice - either refund, repair, or replacement. They replaced it immediately, no problem. I consider STI to have good service.
M.D. Charlton, a S&W warranty station, is great to deal with.
My M&P9 needs a striker. They don't have any M&P9 strikers (because they are back-ordered). S&W doesn't have any M&P9 strikers (that they will sell to me, at least, because they are back-ordered). Brownells doesn't have any M&P9 strikers (because they are back-ordered). My M&P9 has been out of service for over two weeks already, and M.D. Charlton has said that it may be out of service for months. Not their fault of course, the fault is with S&W, but neither would I consider Smith & Wesson to have particularly good service.