I own
the Yamaha HS80m's...I tested them extensively against Dynaudio BM5a's and Adam A7's. I originally went in to buy either the A7's or the 5a's, but after several listening tests I bought the Yamaha's.
The reason I bought the Yamahas is because for the 1000 and below price range they seemed to be the most neutral across a wide variety of musical styles. I basically threw together a CD of stuff that I had recorded and a bunch of songs that I have listened to and loved over the years and knew inside and out. The Yamaha's seemed to be the truest out of the three. That said, I've noticed that the Yamahas present more details than actually translate to my mixes, so while they capture the spirit and the tone of what you are mixing, you have to keep in mind that you may lose some of it in the translation.
The Adam A7's started to grow on me at the end of my testing, and I can really see why a lot of people rave about them. I thought the Dynaudios were really good too, because mixes tend to translate wholly. The Dynaudios seemed to thin out flanges and other effects, though, which would cause me to overcompensate, and the A7's seemed to be a bit too sterile for my taste.
I really love my Yamahas. I plan to jump to something more professional in the next couple of years, but I'm a satisfied customer right now and will definitely keep the HS80m's a second reference set. So far, I feel that they are my best pro-audio purchase.