Welcome to CPF Whomprat.
To quickly answer your question... "I've read through all the new posts and see a couple new lights out there. Is there anything that is really a marked improvement from the L2D? " I don't think so, though I guess it depends on how you define marked.
The lights mentioned are better in some respects, but the L2D became a classic because it was well designed, and I don't think the new ones are that much better. The L2D really raised the bar for the AA flashlight world.
Another brand besides Quark that you may want to check out is EagleTac. They make a few 2xAA models that are also very good. The P10A2 is my favorite. It is the brightest 2xAA production light and has two modes, medium and high, chosen by selector ring so you'll know which level it starts on. No strobe or sos, which I prefer. It is not as versatile as the L2D because of its lack of low mode, but I have plenty of other lights for that.