Here's the thing about the "choice" she gives you. Being turned into Undead essentially denies you any kind of a happy afterlife. Sylvanas saw this when she killed herself and went to WoW's version of hell before she was revived. She constantly moans about how this "curse" is her "burden" but then feels free to force others to shoulder that burden with her.

In Silverpine, a hold out of Gilnean/ Lordaeron soldiers (can't remember which, but they weren't worgen) were killed and raised into undeath. Now, if I were a soldier killed fighting Sylvanas and raised into undeath with free will, I would IMMEDIATELY turn against her. But they didn't. They fought the Alliance.

The Forsaken claim to have free will, but outside of the rotbrain rebels in the starting zone, everyone miraculously serves the Dark Lady and is almost fanatically loyal to her. Even those who are raised into undeath after HER forces killed them.

Sylvanas is an evil person using the Forsaken to further her own goals of achieving immortality. The Forsaken are either blissfully unaware, blindly loyal to a fault, or are incapable of voicing their dissent. Now, I don't think this is a BAD thing. She's an interesting character, and watching her become the thing she hated is a lesson in Absolute Power Corrupts Absolutely. But let's call it what it is, yeah?