I am using Suffusion on 5 different sites and more to come. Same theme all different looks. I am not a 'developer' but I have learned a bit of HTML since creating my own website. The support forum is fantastic especiallly for newbies and Sayontan Sinha, the developer is a hands on person. In this ever-changing world of technology, this theme has been kept up-to-date with W3 and WordPress.org. There are far more options than I will use however that is what makes this theme so incredible. Thank you Sayontan for your dedication to this theme.
Over 870,000 downloads as of Sept 2012 can't be wrong!
When my old free theme became outdated in 2010 and the developer elected not to upgrade I researched many premium and free themes and at the time was looking for only a couple of options that weren't available with the old one. I came across Suffusion and it had the answers I was looking for so I tried it. It is easier to navigate the options now than it was then and that is what makes it so great!
Colour changes, column selection of 1, 2, or 3 on any page or post, more widget areas than you should use, easy to integrate with autoresponders, payment and membership plugins.