Do you ever use it? Are there any pros to using it?   And when?  If your opponents best player is averaging 20 and the rest of the team is avg. less than 10...is it worth it?

i will use it from time to time. usually only if the other team's leading scorer is either by far the leading scorer, as you have described, or if they account for a very large % of the team's 3's OR is by far the best low post scorer.

FYI i run zone exclusively right now

in the early days of HD, the double team - or esp the if leading scorer double team - was very popular.  Often do stuff like go minus 2 and double the best outside shooter

as the engine and learning advanced, it became much less popular

I think it is useful in cases such as jetwildcat describes - also sometimes useful in desperation if you decide to swing your defense plus or minus and want to inhibit the guys who could most hurt you

I use it rarely - like once or twice a season

Sometimes if you have one weak and one strong defender in man to man you could double the player who is being guarded by the weak defender.

just don't do 2x doubleteam. I have seen teams double team 2 or 3 players on my team, and that did not work out. 

I use it alot, particularly if a team only plays one perimeter shooter on the floor. Let's say you're playing in D3 and their best perim guy is an 85 and the rest are in the 65-70 range. I would definitely doubleteam the 85 perim guy and play a -2. It really does leave somebody wide open, but I'm willing to take that if I can guard the inside (plus rebound the ball better) AND eliminate their best outside threat at the same time. 

This example is one where I probably have the inferior team, although it's very, very close, where I doubleteamed NMH's best three point shooter and sagged and it really crippled his offense. One thing that I would add is that I very rarely doubleteam in D1 (big 6) simply because the rest of the players will absolutely shred you if you leave them open since the talent is so high. 

http://www.wisjournal.com/hd/GameResults/BoxScore.aspx?gid=6713975

I use it quite a bit.  Things I consider are: IQ of the guy I want to double; his passing rating; his assist/turnover ratio.  I also consider the D ratings and IQ of my guys.  What I would love to know is who is the player on my team that is doubling.  Ex.  if I want to double a SG will it be my PG or SF?.  Likewise, if I want to double a PF will it be my C or PF?  Would love to know how the engine determines this.

It's exceptionally useful vs. teams that push their distrubution rediculously high on any on particuar player as well.