The memory card issue was on my mind too, but in the opposite direction. I had three professional level SanDisk CF memory cards for my D300, a 4MB, and two 16MB CF cards. If I was to go with the D600, I would need to buy all new memory. I could still use CF with the D800.
Worse yet, I will probably need to thrown in the three CF cards when I sell my D300 to make the sale more attractive.
But fortunately B&H had a D600 package under $2,000 that included a professional SanDisk 16GB SD card. It also included a very nice camera bag and a backup aftermarket battery. The last time I looked, B&H still has a D600 package around $2,000, but no longer includes the spare battery.
I also purchased a professional SanDisk 32GB card for around $65. This works out well in the D600. I have the 32GB in the primary slot and the 16GB in the second. I set the D600 to write RAW files to the 32GB SD card and Fine JPG to the 16GB card.