My LED sidelights (the original ones James mentioned at the start of this thread) have started to misbehave... or rather one of them has.
When I start the car, the bulb warning light has started to come on briefly, then goes out again after a few seconds most of the time. But about 20% of the time, the light stays on and the driver's side LED goes out (if they're switched on at the time).
It's annoying enough for me to want to change them asap - I don't like having warning lights on the dash.
I've ordered some alternative LED ones for now (the Mtec LED sidelights with a separate plug and play resistor cable, from hidsdirect iirc).
If I see problems with the new LEDs, I'll be grudgingly returning to glass bulbs of some sort.