Yes, I've been collecting ML for years. I've focused on X-Men characters and villains, but I'll admit that I've bought a crap-ton of other figures just for the BAF parts. I have a lot of avengers too. Looking back, I'll bet I have about 70% of the figures they've ever produced.
I don't have the new Jean Grey yet, but Archangel is pretty sweet.
Which ones are you planning to get?
I skipped buying figures I didn't want and just bought the BAFs that I wanted complete off eBay. This was 4-5 years ago so they weren't as nuts.
So far, my Avengers team is pretty sparse. I've got classic Thor, movie Iron Man, classic Cap, movie Hulk (the ML wv1 with the Norton-Hulk head, got it on clearance at Target for $6) and I'm considering getting Quicksilver, Scarlet Witch, Vision, Black Widow, and the upcoming classic Hawkeye. I'm not a fan of Pym or Wasp, but I kinda need those two, I guess, if I get the others.
Loners I've got are Movie Spidey, movie Doc Ock, Venom, Punisher and Deadpool.
BAFs I've got are 1.5 Sentinels (the half came from the carded figs I bought from that wave), Blob, and Apocalypse. I've considered finishing the other Sentinel but think it'll be impossible. Problem is, only 2 of the 3 parts I have connect, and they don't look cool.
X-Men I've got are Xavier, Jim Lee Cyclops, 2 versions of the tiger stripe Wolvie, green Phoenix, Gambit, Rogue, Storm, Iceman, Colossus, Nightcrawler, Psylocke, red Angel, Cable, Bishop, Beast... (All in Jim Lee deco) and the new Archangel and Jean (Jean arrives today). Villains I've got are Sinister, Sabretooth, Magneto, Juggernaut, Mystique, Pyro, and then the BAFs I mentioned.
X-characters I am considering are: Quicksilver, Scarlet Witch (these two I can't decide if they'll be Avengers or villain deco/affiliation), Omega Red, Forge, Shadowcat and regular scale Apocalypse. I've all but bought brown suit Wolverine, because I think that's the best sculpt of him so far in a deco I want.