It will depends on your USB ports. I use 2.5 GbE USB adapters and they work great... as long as they're in the right port. Half of the ports on my Thunderbolt

It will depends on your USB ports. I use 2.5 GbE USB adapters and they work great... as long as they're in the right port. Half of the ports on my Thunderbolt dock are provided by a shaky ASMedia USB chipset and it drops or lags after an hour or so. The other half of the ports use a more solid Fresco Logic chipset and I left an iperf + ping running overnight and it was a solid 2.3 Gbit 0.x ms the whole time. The built-in Apple ports are also solid.