I like the "expansion" model, where there's a series of large DLCs, maybe half or more the size of the original game. A developer makes a game. If it does poorly, that's it, and they don't do expansions. If it does well, they make and sell expansions until sales fall off.
That lets people get more of what they want if it's good, doesn't force all of the money to be put in place up front, but also doesn't constantly shovel ads in your face.
I could hypothetically imagine microtransactions that I like, but in practice, I haven't seen anything that looks either appealing or cost-effective. Frankly, the smaller the value of the item, generally the less cost-effective it seems to be.
The only significant "small" item I'd like to get -- that no developers seem to provide -- is more music in some games. Like, GTA or Fallout: New Vegas radio stations.
I will concede that for people who play MOBAs or similar online games, where a single game is played an enormous amount, and they stare at the same character for ages, that buying cosmetic items for that character might make sense, to keep the visuals from getting too stale. I don't really enjoy that genre, but if I did, I could see that being worthwhile.
The only times I can recall DLC content really being memorable was in the expansion form.
I'm also a little annoyed that Steam doesn't have a way to let one (optionally, on a per-title basis) be notified about new DLC for titles that one owns. I think that that'd help encourage expansions, which otherwise might not get as much attention.