I use these headphones for pretty much everything from monitoring, tracking, and listening to music outdoors and it does a very good job in all situations. The semi-open construction is useful for being able to hear traffic while in urban areas, which is usually difficult with closed-back designs. Unfortunately, that means there is not much rejection when tracking loud instruments like drums or a miked guitar cabinet in the same room.
The sound quality is great, but not as crystal clear as my AKG K-702 but these AKG K-240s are a fraction of the cost. The character is nice and clear but doesn't have an anaemic or over-present bottom end; The bass and low mids sound pretty good to my ears.
The construction is actually a lot tougher than it would appear, but beware that AKG headphones sometimes have a problem with wires popping loose inside the housing. Repairing this issue requires opening your headphones and re-soldering the loose wire. This has happened on 2 of the 3 AKG headphones I own. Also, the soft, plastic ear pads harden over time and need replacing. That being said, these are some of the hardest wearing headphones I've ever owned.
I highly recommend them to anyone looking for great value headphones that will serve them for years with the minimum hassle.