A couple weeks ago I decided to finally make the move to using Firefox as my default browser. The main reasons I hadn't done this before were the fact that the product I work on has been largely IE-centric and some of the services and sites I visit frequently still aren't optimised for non-IE viewing.
Fortunatly, due to some clever guys in Taiwan we have IE Tab, a handy extension for Firefox that, with a single click, switches the current browser tab to the IE rendering engine. Now if I want to work with IE I just open up an IE Tab directly in Firefox and away I go! Great for Windows Live Mail (the successor to Hotmail), which is STILL hobbled for non IE users!, and development testing! Now If they only did an "Opera Tab" 
Another cool feature is the ability to create a list of sites and have Firefox automatically switch to IE Tab when rendering them. Innovations like this make switching so much easier can certainly do Firefoxe's uptake rates any harm… Great stuff!
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