As said in the other thread:
I started with the D&D Basic Set edited by Frank Mentzer w/ Larry Elmore cover art. My best gaming-friend had the D&D Basic rulebook edited by Tom Moldvay w/ Erol Otus cover art. When we were ready for the Expert Set I got the Cook/Marsh/Otus book and he got the Mentzer/Elmore set (i.e. we both had mismatched sets) and didn't realize until years later that there were actual textual and rules differences between the editions besides just the art.
(It's probably pure nostalgia talking, but I actually still prefer my mismatched combo of the Mentzer Basic and Cook/Marsh Expert sets -- I think the Mentzer set provides a better pure introduction to the game (via its "choose your own adventure" intro and extensive DM advice) than Moldvay, but I like how the Cook/Marsh Expert rules feel like more of a "complete game" (with characters maxing-out around 14th level) whereas the Mentzer Expert rules with their shallower power-curve (slower progressions of saves and thief skills, some high level spells and monsters held back) are designed with more of an expectation that you'll eventually continue on to higher levels and additional rulesets (Companion and Master).)
I missed the second part of your question the first time around: at present I'm not planning to pick up 4E (just like I didn't pick up 3E or 3.5E). Between OD&D (my favorite), 1E AD&D, and the various Basic/etc. sets I feel more than sufficiently set with D&D.