I purchased an E2D (Incandescent) and was disappointed at the low usability of the spill. My EDC light (Quark mini 123) not only had a superior beam, it was far smaller and cheaper. Well that just wouldn't do! I went searching for a drop in replacement and ended up buying a Veleno designs LED drop in (single mode) based on recommendations on this forum and couldn't be more pleased. I don't know if they're still available, but if they are it's an upgrade worth pursuing.
If I had it all to do over again I probably wouldn't have gone with the E2D in the first place... While I love the size of the E2 series, considering the cost involved of buying the host then upgrading the LED (about $160 total) it's just diminishing returns. It's rugged though!