Before I begin the review I just want to point out that this was no lost episode. This was actually the series finale episode of Ben 10. It's probably considered a lost episode because they forgot to air it.
Overall the finale was passable. This could have easily have been an hour episode (and would have been better), but they decided to turn it into a normal episode. The final fight against Vilgax could have been a lot better and more planned out. On the positive side though, this wrapped up things just enough to make us want to watch 'Alien Force' (which actually isn't a bad thing).