Pros: Know the Sennheiser name. Have them for home. Love the sound. Comfortable. Well made. Stable during wear. Good price, received addl off (limited time). Even without the addl off, the retail price in my opinion is fair. I would love to hear through a studio model, I'm sure I won't be disappointed when I get the chance.
Cons: Do not fold, limited color (just black). But these things are easily sacrificed for the sound that Sennheiser provides.
Summary: I used these cans direct from my MacBook Air 11.6" headphone jack. I played lossless songs using Amarra + iTunes. Very noticeable is the deep full bass and spaciousness. While obviously slightly veiled, the music was very pleasant. The tonal balance across the spectrum has good balance. Nothing really jumps at you in terms of presence. The bass slam and percussive attacks are a bit weak. Snare drums and cow bells tend to be drowned out.
Summary: I bought this pieces a few weeks ago during a special and for the amount paid (80 usd) they deliver.
Like any open-back headphone they are awesome with soundstage. They are the most comfortable headphones I've ever had. Only real downside is that they are really underpowered by an Iphone. For instance, with my Klipsch S4 with 50% volume my head is about to explode in heavy noisy environments, with the HD239 not even at full volume I get to hear them decently.
Pros: Very comfortable. Amazing soundstage
Cons: Retail price is a bit on the expensive side. Underpowered when playing with an Iphone w/o an amplifier.