This is an important factor. In my case, I am using a direct connection from my model M by use of it's ps2 connector. However, I also know that when the day comes when I have to upgrade the motherboard on my home built PC, I will definitely not have a ps2 to plug in my model M directly and will HAVE to use an adapter. As many here have stated, there are both good and bad points (not that many bad) to going in either direction. You really can't go wrong whichever way you go. Both are great keyboards.