If I'm being honest, costumes and some graphical upgrades are very much a simpler proposition and I wouldn't be surprised if most of the new content was along those lines. Most of all, I just want the same quality of models from the cutscenes in the main game, since the new systems can certainly handle that. It's pretty clear from the hair models that they were trying to cut alpha-sorting out of the rendering pipeline during gameplay, most likely for performance on the PS3 and Xbox 360 and mid-range gaming PCs (in 2008).
I think the main disconnect I see around the forums is that we think of things from a fan's perspective more often than we see it through the eyes of Capcom in Japan. I imagine having 'merely' playable Vergil in DMC 4: SE sounds like a much larger value proposition to them than it does to many of us. I would be happy with more, certainly, but if all I get is DMC 4 with Vergil, that'll be enough for me to relive it, cutscenes or no.
I think the price is the only real issue, here, since 40 USD still feels like a bit much when I have the PC version. Also, I've been playing it with the PS4 controller on PC and it's definitely an improvement. If I'm being honest, this is a decent strategy, since there aren't many (any?) good hack n' slash games out for PS4, yet, so they'll be in the market just in time to capitalize on the drought before we get some decent titles over the next couple years.