As the slight edge says, everything has an impact. Dragonfly spikes are either faster or slower than any other spike. Any spike you look at is either faster or slower than another. Now, is it dramatically faster? No. People claiming the '1 second per 600 meters' thing that Nick Willis said, I think that's a bit drastic. I'd be surprised if it was more than 1 second for 1600 meters. Otherwise a lot of people are actually running kind of slow right now since their new spikes should make them 2.5 seconds faster per mile. Lots of people aren't running those new times.
Anyway, if you ran a 1600 your spike choice isn't going to makeup several seconds, I'd be shocked if it changes your outcome by more than one second. Or two seconds in a 3200.
If the new Nike spikes were dramatically faster, then in professional races where most the athletes are within a few seconds of each other in an 800 meter to 3k race, then all the Nike shoes should be at the front. But we're not seeing that, plenty of Adidas/New Balance/ or other shoes are still winning races and setting records. Hoppel just broke the American record for indoor 1k. According to Nick Willis he would have run 1.66 seconds faster wearing dragonfly spikes. YEAH RIGHT! Hoppel wasn't about to run 1:14.6 in an indoor 1k this year.