Regarding wildcard usage I usually save mine until after Christmas, although with the extra one you get nowadays maybe not so vital. Like the guy above for me it is usually to try and exploit DGWs - in fact last season I think I used my main wildcard to setup for a DGW, and then used the winter wildcard to 'fix' the team back to something for the rest of the season.
One thing that is worth noting is that if you use your wildcard really late in the season arguably you don't get much benefit from it i.e. if you play it in Week 3, then potentially you get 35 weeks of benefit from it, compared to only 6 weeks if you play it in week 32.
Personally I steered clear of RvP in preseason because I wasn't sure where he'd end up playing and all my transfers to date have been fire-fighting rather than tactical changes (getting rid of a Villa player who isn't getting picked, getting rid of a Chelsea player as they weren't playing this week, and getting rid of VdV as he's left the league. I also felt although arguably the best player in the game he's also the most expensive.