Just how bad are bottle dynamos? My tourer has a dynamo front wheel, which is great.  It's so handy* that I ended up using it for most of my commuting over the winter, despite having a hybrid that should serve as my foul-weather commuter.  So I'd quite like to add a dynamo to the hybrid which does a few tens of km per week.  The budget simply isn't there for a new wheel** (or rebuild, but the rim is old) plus lights, but a bottle dynamo from a reputable brand is only around £/$/€12 and my tyres (marathon plus) already have tracks.

Bottle dynamo vs. hub dynamo covers some of it (longevity, tyre wear), but I'm interested in day-to-day reliability as opposed to longevity, i.e. can I just jump on and the lights work assuming I don't clobber it? In all weathers? I can with the hub system and this isn't addressed at the linked question.



* Clip-on lights (the vast majority of battery lights) get stolen where I park (and I can't change that) so have to be removed.

** I will downvote any answers that mainly suggest a hub dynamo.  I know they're better in many ways, I know you can get a wheel for ~£100 delivered, but that's too much. Unless there's an option that's similar in total price to a bottle, forget it.
Bottle dynamos aren't actually as bad as often claimed. They are usually cheap, lightweight, have less resistance than people think and zero resistance when not in use. There are some bad parts, though:


Most of available dynamos are complete rubbish and won't last in use. High quality dynamos have been superseded by hub dynamos and battery lights.
Resistance is still higher than with decent hub dynamo
They are noisy and the pitch depends on speed, making any slowing down obvious
The cable connections are often very unreliable (see "complete rubbish")
The clamps damage finish on the fork. Some systems use fork and frame for ground and depend on puncturing the finish, preventing putting any protection between clamp and fork. This also doesn't work with carbon forks.
The dynamo is in perfect position to fall into spokes and can cause serious accidents if not properly installed. It is also easily knocked into spokes, so you have to check every time if you leave your bike in public place.