Good until the last season - the worst last season in television history
Did the writers just phone in the last season or what?
Arvin spends most of the season doing anything/everything to heal his daughter - who many fans love. Then in the very same episode he accomplishes this, he chooses a manuscript over her, accidentally killing her in the process - after so many episodes building up how much he loved her - and she loved him - and happy fans because she is OK. Now she follows him around as a ghost with complete hatred. Would have been better if she died of the disease at the end of the previous season.
Vaughn is killed - everything and everyone not giving so much as a hint that he's still alive. There is even a whole episode devoted to her having to give him up. Then *bazinga*, Sydney and Jack nonchalantly discuss the fact that he has been alive the whole time. No build up to this whatsoever. Could this really have been the writers' plan all along? Was Michael Vartan not available to shoot any season 5 episodes and then his schedule changed and he could? It just makes no sense.
Several seasons are spent rehabilitating Sloane. I assume many (most?) of the fans really start to like the guy. The actor who plays him does an incredible job. Then the last half of the final season turns him into the most evil character the show has ever had and he basically ends up in an earthly version of hell.
We have an entire earlier season where Sydney's mom is essentially rehabilitated and does everything she can to help her daughter. The actress quits the show or is simply written out. The story is that Jack kills her for trying to kill her daughter. Then we find out it was actually her aunt that tried to kill her and Sydney dramatically rescues her (miraculously still alive due to the ever present doubling technology - the double was killed not her) and all is well. Happy family reunion. They will all live happily ever after. No wait - she is just as evil as Sloane and tries to kill her daughter in the final episode. WTF?
Also, the final season introduces a new Rambaldi endgame - funny I thought Arvin had discovered the endgame years earlier when he was pardoned - no wait, the endgame was the ball that made people zombies - no wait it's something else - so he finally gets to Rambaldi's tomb - which for some reason is in Mongolia despite him being executed in Italy. He starts some miraculous process for achieving eternal life - surely he will use said technology to bring Rambaldi back to life - assuming the rose guy from the Italian prison isn't Rambaldi (after all, wouldn't have Rambaldi given himself eternal life?) - who that guy is is forever left a mystery; or certainly he will have brought his wife and daughter's body to the tomb so he can bring them back to life without delay - nope and Sydney stops the process right in the middle - yet Arvin is still able to come back to life. And yes Arvin knew the 3rd? endgame was eternal life - he wasn't the least bit surprised when he was healed - and he knew he had achieved immortality.
Honestly, I felt like the writers had it in for the fans and decided to just pull all their teeth out - Chinese torture guy style - just for the fun of it.
I wish I had just skipped the last season. I've never been more disappointed in a final season.