Well, maybe not a positive spin, but at least a less negative one:
From what we've seen in 4e, being a defender will suck a lot less. In 3/3.5, defenders were vunerable to a lot of save or die/suck effects (due to generally low will saves) and they also had no particular defense against things like touch attacks (since they had to get up close to deal damage), and were sent into a agonizing spiral of a) sucking and b) doing an obnoxious amount of math by ability drain (which the aforementioned touch attacks made them vunerable to).
Additionally in 4e, flying is going to be a lot rarer (at least at low levels), so the days of the melee fighter who is more or less impotent against a 5th level wizard (with fly and protection from arrows) should be over.
In the actual positive side, defenders are going to get some amount of battlefield control (stopping other creatures from shifting, shifting themselves or party members as a result of power), which should give them plenty of interesting things to do in combat, maybe even more than the wizard. In the 4e demo I played (not an official one), but the end of the final combat, the Wizard was pretty much spamming his magic missile for a while after using his Encounter and Daily powers, while the fighter was still maneuvering.
