SharpSetup is used by a number of big companies including LexisNexis (part of Reed Elsevier), OpenText, Iris Enterprise/Advanced Business Solutions, Basler ElectricPhilips as well as many smaller companies.

And what do users think about SharpSetup and its support? Here are a few samples from SharpSetup forum:

This is a great tool. Thanks! (link)
Works really fine with your explanation! Thank you for the great service! (link)
I really enjoy using SharpSetup! Excellent approach used here. (link)
Thank you tomasz_grobelny!! It perfectly works now! That was a greate hint. (link)
Congratulation, well done! I tested version 1.4 to generate a fully localized and functional setup and I ended up successfully. You did a good job! (link)
Thanks for your reply that is very reasuring. I will be recommending we use SharpSetup for our product installers. (link)
Thanks for your help - great product :) (link)
Your new version fixed the problem - thank you for your extremely quick support! (link)
Works perfectly! Thanks ;) (link)
What does extremely quick support mean? It means that in most cases you will receive useful answer within 24 hours after posting your question. You can go to the forum and check the dates for yourself.