DEFINATELY more brightness, better runtime and reliability. Other than the freaky initial drop in output (which is more of a glitch in initial output than an actual drop) it basically runs for a day before dropping to a still usable amount of light. With the incand bulbs, you get a couple hours of the decent brightness and another 3 or 4 hours of sadly dimming output.
To give more detail about the dropping in output -- that's based on heating. The maglite body, since it consists of a spring-loaded pedestal surrounded by a plastic cammed reflector, there is no heatsinking path. In order for the LED to protect itself, it dims the output as the LED heats up. The LED driver is running the LED at lower power,it's not that the LED is getting less efficient. Nonetheless, even at its dimmed output, it will still be significantly brighter than the incandescent bulb by a fairly large margin.
Also, If you can find a module that is based on Seoul Semiconductor LEDs, those are double the efficiency of the Luxeons used in the MagLED with similar beam pattern, so they'll be even brighter still. Some on here have actually replaced the MagLED with a Seoul LED themselves and doubled the brightness (though this would take a fair amount of finesse to pull off without destroying the lamp) I think Terralux makes SSC emitters forr 3-4 cell maglights, I'm not sure if it's possibel to get one off the shelf for the 2 cell lights yet. SSC could give potentially give you greater brightness than the Xenon bulb for days straight.