One advantage of electric kettles over stove top is that they can be
easily brought elsewhere to heat water out of your kitchen. This may
be good for gongfu brewing, where you use small amounts of water
frequently but don't want to stand at your kitchen counter. I also
use one I bought from adagio in my office at work and it functions
very well. It has an adjustable thermostat and I can set it up so that
it either shuts off right after boiling or something relatively far
below that. I have one at home that boils for ten or so seconds before
shutting off. That one is harder to cool down, but you can always stop
the process before the boiling occurs if you are paying attetion. The
other good thing about electic kettles is that they generally
automatically turn off, so if you put the water on and forget about it
for some reason, you don't have to worry about burning your house (or
office) down. I remember a time when I put a stovetop kettle on and
then forgot about it and left my home. Luckily, it was a high end
calphalon pot that was sturdy enough to withstand (somewhat) being
heated empty on the stove for several hours. Otherwise, I could have
easily burned my house down. Regarding speed of heating, mine are
faster than my electric stove, but I'm not sure how they would compare
to a gas stove. But I'd say there are many other reasons to buy such a
kettle other than speed.