I'm going to buy an XBOX 360 just to get Final Fantasy 13.
That's dumb.
Seeing as it's for PS3 also, and that the PS3 and 360 are the same price now, get a PS3. It won't RROD on you, and it plays blu-ray movies without an add-on.
I'm waiting on Square to announce a PC version. It's already largely PC ready due to the method of creation, all it needs is optimization and assorted added options, like with the Last Remnant.
Also, technically the console ports are being released first anyway :P (Yes, they're ports. Squeenix uses a PC-based coding and creation method that is then ported to code the consoles can interpret and use).
I don't have an HDTV so that defeats the majority of the purpose for getting a PS3. I also do plan on getting more than just FF13 and I like the 360's selection of titles better.