I despise websites that do this because I have to use IE7 at work. This is probably the second fastest way for me to banish your website from memory besides being spam. Everyone on here talks about making the sign-up process as easy as possible, and requiring someone to download and install an entirely new application is about as complex and uninviting as one can get. Us "technical" people are still people, and the m…
Yes, but it's not usually one bug. A bug here and a bug there and pretty soon you're talking about real money. IE7 isn't so bad but I'm seriously contemplating dropping support for IE6 very soon.
Just supporting the way various sub-versions of IE6 inconsistently handle cookies is a nightmare, and in many cases lead to unsolvable issues. This costed a client of mine real $$$$ to discover, and less than 20% of their audience used IE6. Less than 15 people actually complained about the issue.
IE 7 isn't quite as bad, but it still adds a measure of time to front-end development efforts. I would estimate it in the range of 10-20%, depending on how complex the interface is.
On two recent projects, we dropped IE6 support, with virtually no push-back from a general-use audience. IE6 is almost 8 years old. Most people don't keep their cars that long, and can understand that an old crusty browser is not going to perform as well.
The only place where I would be hesitant to drop IE6 support is on marketing sites (where you need to entice someone to a call-to-action within the first 30sec-1min) and on e-commerce sites, where every dollar counts.