firefox -- works best for me, no problems with rendering websites i visit, displays all types of multimedia, the flexibility, customization, and utility are unmatched by other browsers.
no need for other browsers but have tried/used many --
safari -- used for testing website compatibility. it doesn't display/render all pages/sites and just doesn't work for too many sites with multimedia to use as a primary browser (and flash sites break more frequently with safari and there still are plenty of them around).
omniweb -- fastest of all the mac browser on my mbp (even faster than chrome) but don't care for the side tabs and can't move them to spread across the top.
chrome -- the browser is fine but makes you sign in to get extensions (that's unnecesary)
opera -- fine but nothing special
seamonkey -- works fine, like FF but more integrated features
camino -- showed promise but development has slowed and is clunky by today's browser standards
To the OP, your website should recognize that i'm using a mac browser and when i click on the download button should download a suitable installer -- i got an exe file -- that made me question the company and the technology. Once i got the mac version, no faster than other browsers, displayed/rendered pages fine, however, there's no way to type in a URL (or URL fill in) so it's a no go for me as there's nothing beneficial about it and it's inconvenient to have to search for a site instead of typing the URL.
Thats only for "Web Apps"