I got the 64gb version in batch one, and immediately upgraded it with a 256gb ssd I had laying around from another system. It was pretty easy, and flashing the OS was trivial even in those early days, but I did find it difficult to get the EM shield to go onto the drive that I chose... It was a tight fit and took 10 minutes of tinkering to get it on there.
It's turned out to be nice to have the extra internal space for doing things in the desktop mode (especially tinkering with emulation) just because, while the sd card is seamless for steam libraries, it adds some complexity and headaches for other software.