Jago23 said:
...Does anyone use dynamo systems for their bikes ..
Yes, on the beater. No maintenance, always ready for action, and on short runs the extra drag of the dyno isn't a concern.
Jago23 said:
...Does anyone use dynamo systems for their bikes and if not, why not?
Not on the commuter or the MTB. Not having a hub dyno I'm not about to put up with the extra drag for the commute, where speed is of considerable interest to me. Besides, parts of that route is so poorly lit that I doubt if any dyno could cope. Not on the MTB either, tech sections drops speed below what's required for good dyno action and lots of light needed.
Jago23 said:
...Is the ..cost of running a bicycle light really a problem?
Depends on what your requirements are. If you're riding well within your ability and only want to comply with legal requirements and perhaps have enough light for modest speeds, then cost is not much of an issue.
But if you're riding hard in the dark it becomes another question entirely. High performance systems comes at a significant cost, particularly if you want to keep the battery weight down.
Jago23 said:
...Is the power source ...really a problem?
Depends on what your requirements are. If you're riding well within your ability and only want to comply with legal requirements and perhaps have enough light for modest speeds, then even a crude bottle dynamo would be sufficient. Disposable batteries can also last long enough to be a working solution if your requirements are simple enough.
But if you're riding hard and fast when it's dark and cold it becomes another question entirely. At a 2nd thought, slow and hard can be equally difficult.
Steep climbs and difficult trail passages can drop your speed to the point where dynos don't work very well, your tires can pick up sleet/mud which causes bottle dynos to slip ASO.
Hub dynos have gotten a good rep, but if you didn't know you wanted one when you got your bike they will require a wheel rebuild or a new wheel. And maybe you want something more from your hub (holes, brakes axles...) than the hub dynos can offer?
Rechargeable systems needs to be recharged, which might be an issue if you're into unsupported touring, or if you regularly store the bike at different locations. If you're commuting you might need a charger at each end, or carry it with you on every ride.
Then there's the question about how you like your bike, some people will be happy with a rather permanent light setup on their bikes, others will prefer something that can be easily removed on "race day" or simply when it isn't needed. Some will insist on easy removal to keep the bits from getting removed by someone else...
What I'd like to see (more of) are small and neat bike powered lights that are sufficient to comply with legal regulations. These can be left on the bike permanently, and then I can attach/remove the riding lights as I see fit.
One idea that I find tempting is to see if a piezo crystal in the seat post could generate enough energy to power a rear led blinky for instance.