I only ran a few tests w/the xpert, because, well, a state of the market-type report on a discontinued stove just wouldn't make sense. For what it's worth, though, in one "deep-freeze" trial the Powermax/xpert took about 21 minutes to boil versus about 7 minutes for the Primus, 7:45 Simmerlite, 10:00 WindPro, 11:45 Reactor. In one of the more "general" test runs, the Xpert took about 9 minutes longer than the Lander to boil on slightly less fuel.
Damien, don't know what to tell ya. I ran the Reactor empty, several times. Shake it, nothing in there. Weigh it, nothing in there, open it, nothing in there. I'm not concerned about theory, just what is recognizable and usable in the field, and the only way you could've told whether there was technically any amount of fuel left in the canisters would have been with a gas-sniffer and a microscope.
EDIT: Oh, Doug- the other Primus would be the Express Spider, the remote canister version of the Lander. This article was conceived primarily as a white gas stove article, and for the comparison of canister stove: white gas I chose to go with two well-known, nearly identical models for comparison. But yeah, it would be interesting to also compare the Spider to Lander.