So when you consider the warranty issue, all you have to do, is throw a number of extra bucks at your Dell, to get longer, and, if you want, wider coverage.
The Dell 2400MP lacks a DVI input, but that's found on very few projectors in its price range, and is only needed by an even smaller percentage of the market. More to the point, however, is that the Dell has only one computer input. If it has a real failing, it's that it doesn't have a component video input as well. You can feed the Dell a component video signal through the computer input, but that means you if you want a computer hooked up, you can't also have a top quality (digital or component video) source hooked up at the same time. Interestingly the Optoma TX700 which was one of the other projectors reviewed for the comparison, and one not quite as bright, has a DVI port with digital and analog, plus the usual analog computer input, providing the for excellent flexibility. If you need computer signal plus component video, or digital, you might consider that Optoma.
Lastly, the 2400MP is a bit noisy. In full power, it is definitely audible but shouldn't pose a problem, even in small rooms. The 15% dimmer eco-mode is an easy alternative if it's noise is a problem for you. It doesn't quiet it much, but probably enough to satisfy just about everyone. Many other small powerful projectors, that come to mind, like Epson's 765 (2500 lumens, 4 pounds), are significantly noisier.