example: HS

In OS X, USB Prober.app will tell you the speed of the device:

High Speed device @ 4 (0x1A120000): ........................   Composite device: "DataTraveler 2.0"

You can capture the descriptor, etc, by starting ovctl before plugging the device in:

$ ./ovctl.py -p ov3.fwpkg sniff hs
[   F    ]   0.267814 d=  0.267814 [   .0 +267814.250] [  0]  
[        ]   1.123487 d=  0.855673 [255.7 +  0.600] [  3] IN   : 2.1 
[        ]   1.123488 d=  0.000001 [255.7 +  1.250] [  1] ACK 
[        ]   1.224924 d=  0.101436 [101.2 + 54.550] [  3] SETUP: 2.0 
[        ]   1.224924 d=  0.000000 [101.2 + 54.967] [ 11] DATA0: a3 00 00 00 02 00 04 00 f6 e1 
[        ]   1.224927 d=  0.000003 [101.2 + 57.933] [  3] IN   : 2.0 
[        ]   1.224928 d=  0.000001 [101.2 + 58.633] [  1] ACK 
[        ]   1.224930 d=  0.000002 [101.2 + 60.800] [  3] OUT  : 2.0 
[        ]   1.224930 d=  0.000000 [101.2 + 61.217] [  3] DATA1: 00 00 
[        ]   1.225175 d=  0.000245 [101.4 + 55.900] [  3] SETUP: 2.0 
[        ]   1.225175 d=  0.000000 [101.4 + 56.317] [ 11] DATA0: 23 01 14 00 02 00 00 00 ef 95 
...
# 0000000: 2203 4400 6100 7400 6100 5400 7200 6100  ".D.a.t.a.T.r.a.
# 0000010: 7600 6500 6c00 6500 7200 2000 3200 2e00  v.e.l.e.r. .2...
# 0000020: 3000 ce3a                                0..:
[        ]   1.242314 d=  0.000000 [118.5 + 68.383] [ 37] DATA1: 22 03 44 00 61 00 74 00 61 00 54 00 72 00 61 00 76 00 65 00 6c 00 65 00 72 00 20 00 32 00 2e 00 30 00 ce 3a