Overall, the episode did fairly well. The colors appeared to be duller than usual which gave for an edgy series finale look. It had a striking resemblance to the finale for season 2 and the premiere of season 3. "War of the Worlds" in season 2 saw the bringing together of the heroes found throughout the season to an epic battle. In "The Final Battle", two of Ben's strongest opponents joined forces to kill Ben. Also in "War of the Worlds", there was almost a kiss scene with Ben and Julie, until they realizes how many people were watching them. Fast forward to "The Final Battle" and there is a brief moment of mushiness between Gwen and a restored Kevin. Although it must have been weird since for the latter half of the episode he was only in his underwear. Then the season comes full circle. It opened with Ben v. Vilgax and ended with Ben v. Vilgax and once again Ben kicked butt.
Now, this isn't the end of Ben Tennyson's TV career. The new series is set to air on April 23rd. For the longest time it was believed to be called Ben 10: Evolution. But that was only a working title. The real name of it is going to be Ben 10: Ultimate Alien. I've read a little about what going to be in B10UA from WikiPedia. My main concern, however, is what the aliens are going to look like. There's all sorts of rumors and plenty of what seem to be fakes about the new lineup, ranging from completely new designs to something called "Ultimate Aliens", which are just the aliens Ben had at the end of B10AF souped up. This is rather disappointing for me. I wanted to see ten new aliens, not the old ones on steroids!
At the end of "War of the Worlds", it ended with Ben lamenting over how he didn't "recognize any of these [new aliens]". One new form was actually added after that battle: Lodestar, which replaced the virtually useless Alien X. (Rath was an accidental transformation, and Nanomech didn't show up until Alien Swarm). I'm all for keeping good things going but guys, I wanted to see something new. Actually, I wanted to see ten things new.
Oh, and if you're interested in seeing what familiar plot devices and almost cliche conventions are found in the TV series, I.E. Nazi-like Highbreed (for which I must invoke Godwin's Law upon myself), or Julie the love interest, or the moronic but relatable main character, check out this: Ben 10: Alien Force @ TV Tropes