Something that hasn't been mentioned before in this thread is the weight and drag of rechargeable batteries v. the weight and drag of a hub. I know about this because in the days before there were any grown-up bicycle lamps available (the first ones were BUMM's first series Cyo lamps; the need for rear lamps was better served by Cateye's LD-1000 series well before the birth of the Cyo), I used to make my own superior bicycle lamps from decorator's track lamps available in 6V and 12V in a physical size which glued elegantly into the smallest repainted Roma tomato paste tin, the 6V for the dimmed lamp, the 12V for the main lamp. A two position medical silver-contact toggle switch, of which I had plenty because I used these Swiss items for building up-market tube hi-fi prototypes for the Japanese market, switched the fast-work lamp in and out, and an in-line motion switch switched both lamps on, and a timer cut both out if the bike was stationary for six minutes or so; the 6V lamp was on whenever the bike moved, thus also used as a daylight running lamp. Their reflectors were round, but I cut plastic to glue on to control the cast shape of the light, with a top cutoff higher at the left than at the right so as to see low-flying tree trunks and read road signs -- we ride on the left here, not on the right of the road as Americans do. These lamps, strictly as lamps, were and are superior even to the Cyo on many aspects (utility of light shape on my roads, amount of light, etc), but all the same I abandoned them right smartly in favor of the Cyo when it appeared.
Why? Because the battery bottles hogged cages and their weight dragged even a non-weight weenie like me down, besides which, if I stayed out all night, as I often did (I have an extra-pale skin, so I need to stay out of UV light as much as possible, and I'm anyway a bohemian night-owl), I'd always find myself short of light in the last hour before dawn, just when the farmers and their dangerous heavy equipment start hurtling around the lanes where I ride. Besides being lighter, the hub generator was also positioned lower down, which matters for control in downhill speeding.
So the point I'm making is that anyone in the market for better lamps with recharging on tour, should be comparing like with like: all the weight added by one system with all the weight of the other system for the same number of hours and amount of light. I think you'll discover that the hub generator system offers the most security for the least weight/drag.
Of course any BUMM system will be more expensive than anything you or another manufacturer can build, but that's just the way of the world. Not to mention the ludicrous lack of simple, cheap, desirable characteristics for a lamp on a bicycle, like water-resistance -- over twenty years ago, my DIY lamps above could be used in any orientation and were waterfast to 10ATM for a little thought and a thruppenny O-ring. But hey, it's lèse majesté to criticize BUMM...
PS: I don't think the price will remain at the artificial scarcity level of 350 Euro, but I won't be surprised if it settles at well north of 200 Euro. One wonders what the town health inspector, who did his rounds on a bicycle when I was boy, and on whose cast-off bike ridden to school by his son I learned to ride in return for helping him with his Algebra and Latin, would think of a bicycle lamp, no matter how super-duper, at "well north of [the equivalent of more than 400 pounds sterling back then]".
