Oooh, give in Mikey. I could see not doing DC before because of all the different lines with different scale issues, but now with DCUC you almost have to, especially with ML winding down.
As for the 3.75" stuff, I really hope they screw that up as badly as they did the 6" line. No animosity in that statement, but if the first few figures look like crap, I'll be able to stay away much more easily. 
I feel the same way with the Marvel stuff lately, where I almost hope it will be ending on its own so its easier for me to stay away. Don't get me wrong, I loves me some Marvel, but we do have a pretty spiffy lineup (in the 6" scale) at this point, so if it ends, it ends. Plus, like you mentioned, I don't feel as guilty about devoting money to the DCUC line when there isn't as much competing Marvel merch. out there at the same time.
As for the 3 3/4" stuff, if it is done in the same type of quality as SW and Joe, I'll take a look and likely pick up at least some. If it is re-releases of the SuperHero Showdown stuff, and building on that, probably not. I had a handful of those figures (Spidey, Black Spidey, Ock, Thing, and Cap), and although they didn't look too bad, they fell apart quite easily (and had very loose joints for the most part).
Overall, I should just stay away from all of this - its too damn expensive

. I should have stuck with my original plan (way back when) of just Spidey and Batman "shelves". But then I wanted the F4, and the X-Men, and the original Avengers, then most to all of the Marvel U. This time I want Batman, and the JLA, etc., etc.....

Its all too tempting.