I sent a P320 slide in about 4 weeks ago for a night sight issue covered under warranty. (The front night sight was dead on a NIB gun).
Last week SIG sent me an email asking how satisfied I was for the warranty work they performed. So I called them and asked why I was getting a survey asking about their work when they hadn't done anything yet.
C/S was helpful and said those emails go out automatically but he did check on the status of my RMA. The next day I revieiced a phone call and was able to up grade the sights to SIG X-Ray sights for the price of the sights. I did enclose a letter asking if this could be an option. SIG covered installation and shipping, I'll pay for the sights (full retail though).
Hopefully I'll hear back this week or early next week when they ship it back out. I wasn't in a hurry to get this done, but it looks like its going to be about 5+ weeks door to door.