Next to Kamijou, Hitomi is easily the most hated character in the series, mostly because of her little part in the chain of events that caused two characters to die. But how much of that disdain is really deserved?
For the most part, Hitomi hate comes from shipping. As feminine characters are often regarded as inferior to more tomboyish characters, having one of each competing for the same love interest is never going to end well.
The big question is, was what Hitomi did acceptable? To be honest I'm more upset with the writers for not giving us any indication it was coming. It felt really contrived to have this come up at the absolute worst moment for Sayaka, this being the one thing that would hurt the most. While I would say it was pretty crappy of her as a friend to pop up and say "You need to face your feelings within 24 hours or I'll make my move." But at least she didn't sneak behind Sayaka's back and go after the trash Sayaka was sniffing.
The PSP games do some good and bad for her. On the bad side, Hitomi can behave rather nasty as far as I've seen when she and Sayaka get into an outright confrontation over him. Still not as badly as they handled Kamijou though...
The slot machines don't do her justice either.
On the plus side, the PSP game gave the fans a new ship. Homura & Hitomi. After losing Kamijou to Sayaka, it ends up being Homura of all people who comforts Hitomi. This results in the latter becoming quite attached to the former, to the point that the megucas try to have a strategy meeting but can't because Homura is unable to get Hitomi to leave.
Ship is canon. Though considering this franchise is very blatant and pandering about its shipping, that's to be expected.