In reply to Beano:
It really depends on what you mean by 'lightweight', and what you intend to do with the stove (what you're going to cook, where, in what conditions).
A home-made drinks can meths burner and conical pan support/windshield can weigh as little as 35g, and fit inside the pan it supports. Meths is lighter for shortish trips, since you only need to carry the fuel you need, not a fixed size canister. The container also weighs a lot less than a steel gas canister.
Whatever stove you choose, make sure you use a windshield; make one from a roasting tray or drink can sidewall.
For winter, a gas stove with a pre-heat tube allowing liquid feed is useful, since it makes for better cold weather performance, and prevents preferential burning of more volatile propane in a propane/butane mix.
The Alpkit stove mentioned earlier is a re-badged Fire Maple (Alpkit make no bones about that). Many other companies also re-badge Fire Maple stoves, including Karrimor, available in the dreaded SportsDirect. I bought one of their Alpine remote canister stoves a while ago (a Fire Maple FMS-118), which has pre-heat tube, folding legs and is nice and low profile (i.e. stable). It seems to work fine, even on liquid feed mode.
Quoted boil times are usually measured with the burner 'set to 11'. As such, they are merely a test of how fast the stove can burn gas (aka burner power). For real-world use, a much more moderate setting should be used, with a longer boil time, otherwise most of the heat simply pisses uselessly up the side of the pan. The heat exchanger systems are better in this respect, since they can pull out more heat from the flame (increased surface are exposed to the hot gas).
I'd consider the Reactor to be a heavyweight stove (500g!), but then I'm a bit of a DIY meths stove nutter...