RE: XPS 8900 freezing
I believe I'm in AHCI mode, I'll verify when I get home.
As for the USBs I haven't encountered any issues with those yet. I've had a usb mouse, usb keyboard, usb flash drive all plugged together at the same time in the back panel and in other instances 3 of the 4 front/top ports with an external HDD plugged into the top port.
I have made sure to download intel's software that checks any and all intel devices and the current firmware, everything is up to date.
I haven't touched Windows 7 with this computer yet, if I get home and it's still working that means the fresh install on the SSD has been working for almost 20 hours straight. This computer typically froze once to 5 times in 12 hours...
And from experience I haven't tried other brands, but the logitech unifying devices have worked perfectly for me. I use their mouse using bluetooth, but my logitech solar keyboard has to use the unifying usb receiver, no issues with that disconnecting/pausing. One keyboard is about 4 years old, the other is about 2, both have worked flawlessly even when their charge constantly sits around 40% due to apparent poor lighting.