It's all the 24 nostalgia you could wish for, packed in 12 episodes. All the beats the show had (so far minus irrelevant side storylines and ill-developed characters) back in all it's gloriousness.
It does help that Jack was a prototype that was ahead of its time and therefor doesn't feel dated yet.
Minor gripe: fucking Audrey Raines. Really? Of all characters to return, she is one of them?
Dude, check the pics, she is so much prettier than the girl who plays Jack's daughter.
Also, the daughter was so fucking annoying every time that I wished someone would kill here. Knowing she survives all the way to season 9 makes me want to not watch any more than I've already seen.