I use my own software, XS.
www.lizardland.co.uk
Why I use it... because I know how it works because I wrote it. I know the algorithm works because I've been using paper tables based on it for as long as I've been gas diving. Dr RW Hamilton (who worte the algorithm) is one of the best deco table designers ever and I trust his work.
Yes, I use it because it is free too.
Cheers,
Stuart