I've always went with manual testing. I mean, really, the only browser out there that breaks things is IE5, 6, and 7. Everything else pretty much does the same job. After that, you could test with firefox and chrome which covers 99% of your users (as firefox and chrome use the same web rendering tech as a whole ton of other browsers) followed by Opera.
IE8, 9, and 10 have gotten there acts together and are now pretty standards compliant.