While IE7 (or IE8 for that matter) is clearly very far from being perfect, it's massively superior to IE6. Not just "CSS differences". I mean IE7 fixed bugs like select elements being always on top or the URL fragment (the #hash part) being submitted to the HTTP server as part of the URL. These issues are major pains in the back. Supporting IE7 is an awful lot easier than supporting IE6.
The things you have mentioned are rather trivial in the overall picture and really not a good enough reason to support IE7 but not IE6. The JavaScript engines are nearly identical and the broad set of technologies are the same.
For example, I consider not supporting SVG 10 years after standarization a major probleam. And only IE9 addressed that issue.
While IE7 (or IE8 for that matter) is clearly very far from being perfect, it's massively superior to IE6. Not just "CSS differences". I mean IE7 fixed bugs like select elements being always on top or the URL fragment (the #hash part) being submitted to the HTTP server as part of the URL. These issues are major pains in the back. Supporting IE7 is an awful lot easier than supporting IE6.