Yeah, that's a really inexpensive, simple, and reversable way to dig into a conversion. With a little more effort - and removing the reflector - you could stuff 5 - 7 LEDs in that flashlight. Most of the hobby store LEDs have pretty low light output - they are more suited for indicator lamps than light sources. High-intensity LEDs are easy to obtain via mail/internet order and there is a huge increase in light output. Just food for thought...
The EverLED "bulbs" are real scorchers - I have one in white and one in red, sitting in 2 and 3 D-cell maglites. Pricey, but awesome performance - just puts a grin on my face every time I switch one on. Beats the snot out of the original incandescent - long run time, no dimming, bright, and tight beam.
The two minimag conversions serve different purpose for me (I would not purchase a minimag simply to convert it, but if you already have one...).
The TerraLux roughly equals the incandescent for throw and has more total light output with very useful and difuse side spill - a much more practical torch than the original incandescent in the real world - plus the run time is longer than incandescent. Fits any 2 pin 2AA minimag.
The Opalec Newbeam has extremely useful flood but does not reach way out there - again, it is real-world more useful for 98% of the uses one would put a minimag to than the incandescent. The run times are fantastic - there is simply no energy left in a battery after it is done - this is a really long-run conversion. Needs to be a "new-style" minimag - although I actually converted an old style switch, it's more trouble than it's worth if you have a new style switch available. All well documented in the on-line documentation. Drop lithium cells in and you have a great performing, rugged, extremely long running practical torch that weighs little more than an empty flashlight.
But again, yak with the modders over at CPF - those folks are an awesome resource.
Tom