I'm most worried about Angel. Looking at who they cast as Edward and Stefan (as lookalike as they are right down to the hair), there's just a gaping huge chasm between these types of younger-feeling, less Alpha, less intimidating personalities that feel like they were trying for softer and cuddlier versions of Angel, but palatable for much younger girls. Buffy's taste in men in general (well, the ones that she was with for any considerable amount of time) all feel more mature and masculine than current tastes. The fact that DB went on to play law enforcement and military types and is one for the moms and grannies after the show kind of says it all about his physical type.
I think there's a generation gap here in taste in men. Baby Boomers/Gen-X and Gen-Y/Gen-Z have different ideas (and I'm saying this as a Gen-Y, but one who has almost always favored the old-fashioned men).
Also, the whole straight, white male Alpha trait (Joss talks about feeling he needed to tear Angel down as the only way he could understand the character and had trouble making the spinoff for 5 years because of it) and guys that are going to get girls way easier than him that his shows have been cast with despite his petty hangups (sometimes against his will in DB's case--thank Gail Berman and Marcia Shulman for overriding Joss) is something that has felt like Joss has been itching to attack for a while. I don't really want to see him take out his freaky issues about men (the jocks who used to bully him and the attractive male actors who get laid easier--the latter creepy rant was to James) using Buffy's new boyfriends. I think we can safely say Buffy is not going to end up with his self-insert Xander as he wanted originally by reason of pure marketability of human/vampire forbidden romance soaps that overrode all of his original instincts, but that tendency to see himself as a "nice guy" who is more deserving is something I emphatically don't want to see rear its ugly head.
Seeing straight, white males torn down as either all evil or by becoming the butt of the joke is something that's going to be a real turnoff for me.
I'm also a bit protective of Angel's dramatic, introverted and depressive personality while constantly selfless and his extremely relatable and inspirational falling down and getting back up given that he's one of my bigger identification figures as an Aspie. Joss liking to tear him down and make him the butt of the joke rather than just utilize his lovely deadpan or morbid humor is ick for me for another reason, too.
And I have a feeling that Angel's protective streak (which he shows around many characters), tendency to take his destiny into his own hands that isn't just doing everything Buffy wants and Buffy's source of paternal wisdom isn't going to translate well in the current environment either. Thing is, I happen to love those traits about him. And I don't want to see Buffy spouting off 'don't need no man' stuff. The Buffy I know and love was often seeking out an understanding, wise ear to voice her struggles to and someone she could trust or talk to about things she wasn't comfortable saying to Giles or Willow whom she came for the advice of. The Buffy I know and love was often very sad about how she felt alone with the weight of the world on her shoulders. Angel shouldn't be downplayed as a character who was able to lift some of that weight off and be a hero in his own right.
I don't want this reboot to be afraid of strong, male characters right next to the strong, female characters. If the female characters are written as realistic, varied people who have many personalities (NOT just "feisty"!--Joss at least was always better about this than a lot of crappy writers who seem to think "strong women" means having only masculine traits or feisty), there shouldn't be fear about allowing male characters like Angel, Spike, Wesley, etc... to exist who are also hugely part of the narrative.
Also, I'm a straight female. I feel like some feminist media seems to forget about women who are attracted to men and want to see ones that they'd actually give the time of day to and, yes, fantasize about. Straight women largely don't just want to look at other women!