I might have. When I got the phone I was overdue from Verizon and my Droid X2 was not performing well. At the time my Verizon options were the S3, the DNA or wait a month for the S4. I would have picked the S3 over the DNA because of the SD slot but it was a close decision. The way the question is asked I'm not sure if I should assume the S3 had an SD slot or not, though. If it didn't have a slot I almost certainly would have waited for the S4. If the S3 did have the SD slot I might not have waited and just got it instead. However, if the S4 had a 64GB option I would have definitely got it instead.
Really, the SD slot for me is just a way to make my phone my MP3 player. I'd either need an SD slot or at least 64GB of internal memory to replace my iPod. I have around 30GB of music, so unless I can fit all of it comfortably on my device, I won't use it as a music player. That means 32GB devices are out. If I can't get either then I just won't replace my iPod yet. That's what would have happened with the DNA or a SDless 16 or 32GB S3/4.