I pretty much use what you’ve got there and just wait for the browsers to catch up. Except, one of the browsers (FF or Saffy I forget) can’t use just any px amount for the degrees. Someone was limited to increments of 15 or only certain numbers at all. I forget who and always use the same numbers : )
You cannot use border radius at all for anything that MUST have rounded corners. It’s just an “extra” for people using certain browsers, and since the -mox and -webkit prefixes are actually used for testing while vendors are working on a property, don’t be surprised if one day a new FF or Saffy comes out and no longer work the same with that code.
There is an actual border radius that you could always set after your vendor code. It will be invalid because the validator only looks at css2.1 and under. Whenever browsers begin to support this property it will be “border-radius” itself.
Padding itself shouldn’t be a problem to using images. Maybe post your situation and code.
Once they add support for properties you are able to use them. Assuming of course that you have the proper version installed that has support for their properties.
It is a good option to generally keep up with what the main browsers are doing. If at some point you notice that code not working when you know that they have support for the given property then do some researching. It may be that they changed how you are supposed to use the property.
One of the problems with a specification still being a draft is that it is subject to change but browsers still need to be able to test the current draft in their browser in order to see if the draft is going to work.
That’s what the -moz- -webkit- -op- and -ie- prefixes are for - to allow browsers to experimentally implement CSS that will not conflict with the final implementation if the draft changes in between.