I switched back in April and I thought I should share some of the software I'm now using on a daily basis.
Smultron is a fantastic little text editor. It supports multiple open files, syntax highlighting etc etc.
Shrook is a nice RSS feed aggregator, with a simple well thought out GUI.
NeoOffice is an Aqua port of Open Office.
Mail Scripts whilst not something I use every day I'm including it here as it has some hugely useful functions. These include exports of mail in a variety of formats, linking mail and iCal for sending mail and a host of other handy tools.
I still use Parallels for the one piece of vpn software I cannot use under OSX.
OmniGraffle is bar far the best diagramming application I have ever used. I have saved so much time using this tool, I cannot recommend it highly enough.