The "to host" connection is 25% faster than midi, 38.4kHz versus 31.25kHz. Only thing is it takes up a com port and you can't link up other devices like you can with midi. Unless you're using an external modem or a com port mouse there's no problem. I use a PS2 mouse as well as the built in IBM Trackpoint. The only extra software you need is the Yamaha CBX driver which is fast and takes up very little room. It probably came on your 550 disk but you can dowload it anyway. I'm using the "to host" connection on my desktop as well even though I have a midi connection.

Bryan