2 suggestions: 1) A fallback for IE7 and IE8 (maybe just the main color without the gradient?) 2) A "generate link" button, that basically generates an URL to the current custom button.
I'm pretty sure it's got the fallback (your #1) in place, but let me know if it looks like that doesn't work for you. Your suggestion for #2 is great. I'm not positive I'll have the time to develop that, but I'll see what I can do.
