I can only imagine. They're unusable even in Safari 4 (the reflections turn into white boxes that cover up most of the buttons).
Of course, when you're pushing the envelope, you're pretty much by definition going to leave the laggards who stick to older technology behind.
From the point of view of the user, I strongly subscribe to the school of thought that says build it working for everyone and enhance for the users that have better browsers. These buttons, as the post itself says at the end, are just not ready for production.
I missed the part that says it's not ready for production when I first read it. Here's part of the quote from the end:
> This is just a demo and not meant to be used on your next project that targets the average internet user.
I'm curious as to why he didn't use regular buttons. That would degrade ... (haven't checked the code tho)
I tried his button styles on submit and button inputs. His basic "button" style and the various color and shape variations still work great and degraded well when I checked in IE7.
You can view the results here: http://www.webcodeshare.com/agx3ZWJjb2Rlc2hhcmVyDwsSB1dlYmNv...
Only a small addition was needed to turn off left and right borders.
These buttons don't degrade gracefully at all.