The big problem as I see it is compatibility with Energy Saver, compatibility with USB 3, and drivers.
1. Energy Saver - Many third party USB devices are not compatible with Energy Saver, and won't work unless plugged into a wall powered hub, or until after a reboot once the machine goes to sleep.
2. USB 3 - One of the big running issues with USB 3 is overlapping 2.4 Ghz frequencies with other devices on the same frequency. Cables that are USB 3, devices that are USB 3, and USB 3 ports that are damaged may all cause interference, or be interfered with by 2.4 Ghz WiFi frequencies. You need to isolate it from all WiFi networks, microwaves, land line wireless phones that share the same frequency to determine where the issue resides.
3. Drivers. Older devices made prior to 2011 may not have the appropriate drivers for Intel Macs. Prior to then Apple did not exclude PowerPC drivers entirely thanks to Rosetta's inclusion in the operating system. If your device depends on drivers, make sure it is made for Intel Macs, and not PowerPC Macs and is known to work with Mac OS X 10.7 or later.