Soaking with white vinegar is usually the recommended trick to loosen lime deposits.
I buy the descaler kits from the grocery store if I need to do it. I don't need to do it often though.
I've seen this come up in a number of reviews on Amazon. Some of the plastic kettles seem to give a serious plastic taste to water, even after several boiling cycles.
My kettle is mostly plastic and I can't taste a thing.
The other thing that concerned people is insulation. Is the outside of the kettle too hot to touch? Does the water cool off quickly after the kettle shuts off?
Again, this is with a plastic kettle but yes it is hot but there is a big handle to hold the kettle with. The water takes a while to cooldown.