Even if the money really isn't a problem, I'd say get a third party SSD, unless you definitely need more than 512 GB of storage. If you're comfortable with doing it yourself, great; if not, you can likely find a Mac store that will happily install the drive for a modest fee. Either way you'll save a chunk of money (the best SSDs these days are going for $1/GB or less, nothing close to the nearly $2/GB Apple's charging). Even if you run into warranty issues down the road (which is unlikely, especially if you have a good independent Mac shop), you'll likely come out even, given that you'll be saving $800 (or more if you get a 256 GB drive).
The other advantage to a third party drive is being able to select exactly what you want. If Apple uses the same SSD controllers as it has for the past year or two (and so far that appears likely), you'll get either a Samsung or Toshiba controller. The Samsung is pretty good, it's the same controller they use in their 830 line of SSDs, which was one of the best over the past year or so, but has since been supplanted. The Toshiba controller isn't bad, but it's definitely not great. There are now better SSDs to be had, the best right now is the Samsung 840 Pro (the non-Pro is cheaper, but also worth a look).