I think it really depends on the industry. As an example, the last company I worked at, our main customers were home contractors and other DIY type people and

I think it really depends on the industry. As an example, the last company I worked at, our main customers were home contractors and other DIY type people and IE7 was a large portion of the market share. My best advice is to build a product and check analytics to see how many customers are actually using older browsers. If it's a small group, its probably not worth the effort to make sure everything is ported over. Sometimes it can also be difficult to test older browsers without spending a bunch of time setting up VM's. For my own personal projects, I dont even fully support IE7.