Summary as per above- good bass, easy to carry/portable with folding mechanism and bag, iPhone remote+mic on the left (rather than the right- which is great for those who use their left hand to adjust whilst using right hand on the mouse!), closed ear which is comfortable for me, surprisingly strong build quality which feels like it can endure normal everyday use, ability to use own 3.5mm cable in case you wear the one it comes with out (this has been the death of many fo my previous Sennies), nice packaging, etc.
 
Catch is everyone sees them and laughs especially if in a professional environment/workplace (or if they're an audiophile), and you become a theft target if you use these in public. That, and they're expensive for what it is.
 
Ultimately though, I enjoy them because they are very comfortable on my large head and they block out the noise at work but if necessary I can still *just* hear when someone talks to me, etc. The heavy bass helps put me in the zone.