Before I saw this film, I had only seen the original series a few times, and even though I enjoyed them, I had no expectations of the movie.
If you ARE a die hard TB fan, and are not willing to be open minded, and look at your precious Thunderbirds from a different perspective, then I suggest that you go and buy yourself the original series instead.
I thoroughly enjoyed this film; even though the plot was far from complex, and some of the acting was a bit weak, it was still good to watch.
The film is about the youngest Tracy, Alan, and the tantrums he throws when his dad says he's too young to be in the Thunderbirds. Basically, The TB's get tricked into leaving Tracy Island, and the resident bad guy, "The Hood", and his cronies take over the island. What the Hood doesn't know, is that Alan Tracy and his friend Vermat (The Brain's son) are home for the school holidays, and have been left behind on the island along with Tin-tin (the gardener's daughter). The tree kids must save Tracy Island and their families from the Hood's evil scheme, with the help of Lady Penelope and her driver, Parker.
Lady P and Parker steal the show I'm afraid, although at one stage she did go all Charlie's Angels on us, and I was a little bit worried.
So yeh, relatively good movie, just don't be expecting award-winning acting or a close resembalance to the television series.