I've only made 2 trades involving players in this league, and one of those I consider part of the draft.
During the draft, I acquired Ben Tate and Jermichael Finley for Vernon Davis, a draft pick (Golden Tate), and a 2nd later round pick. There were no good options left for a 3rd RB after Donald Brown didn't fall to me. And although I hated giving up Davis, the trade balanced and solidified the RB position for me and I may have gotten the better TE in the deal.
The other trade was a swap of backup RB's- Thomas Jones for Joe McKnight. McKnight has the upside of youth, but now I have Thomas Jones to backup Jamaal Charles.
So, now I am trying to resist messing with my team unless as the season unfolds I find gaps that need to be fixed. Part of my frustration from my first dynasty league was trading away core players (Drew Brees, Larry Fitzgerald) who helped win me a championship in a quest to build an "ultimate team". The new team scored more points, but didn't win as much high score money, and got upset in the playoffs. So I was left with a bunch of older players on the verge of being untradeable- Reggie Wayne, Randy Moss.
With Pigskin Kingpins I got all of my WR targets- Larry Fitzgerald, Calvin Johnson, & Sidney Rice, but not much depth after them. So right now I'm trying very hard to resist trading one of them for depth at WR (Crabtree, Tate) or improvements at RB (Mathews, Wells, McCoy) since I have multiple teams interested in Calvin. I think I will have more fun keeping my core players longterm and following their careers. By letting my team develop slowly and not forcing the issue, I think that any championships I win will be that much sweeter.
Now, c'mon Megatron! Don't let me down!