Cisco Switch/Router: Collisions, Duplex Mismatch And Performance Problems

I know an IT Manager at a company that was telling me about his experience about slow performance across his MPLS to his remote sites.  He was telling me that he found that his core switch was giving him an "duplex mismatch" message.  He found that his MPLS router (controlled by the ISP) was not set correctly by the ISP.  They were running half-duplex.  This was causing performance problems and he found the following on his core switch interface (connect to the MPLS router).  Notice the collisions:

GigabitEthernet2/0/1 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 2c54.XXXX.XXXX
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 61/255, rxload 3/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Half-duplex, 100Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:17, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 977147969
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1223000 bits/sec, 460 packets/sec
  5 minute output rate 24292000 bits/sec, 3800 packets/sec
     1980578959 packets input, 615394171190 bytes, 0 no buffer
     Received 381332 broadcasts (334480 multicasts)
     0 runts, 1 giants, 0 throttles
     4 input errors, 3 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 334480 multicast, 0 pause input
     0 input packets with dribble condition detected
     14455682756 packets output, 9820573157817 bytes, 0 underruns
     0 output errors, 46438986 collisions, 1 interface resets
     0 babbles, 199866683 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out

So he called up the ISP and told them to make the changes on their router interface to be full duplex.  They did and he reset the counters on the core switch, and you see the results below.  Better reliablitiy.  Better performance.  And no collisions on the interface.

GigabitEthernet2/0/1 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 2c54.XXXX.XXXX
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
     reliability 255/255, txload 5/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:26, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:00:47
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 1129000 bits/sec, 388 packets/sec
  5 minute output rate 20433000 bits/sec, 3134 packets/sec
     13547 packets input, 4241997 bytes, 0 no buffer
     Received 7 broadcasts (1 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 1 multicast, 0 pause input
     0 input packets with dribble condition detected
     161684 packets output, 142796555 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out