I liked it...(spoilers)
...Ok so its got more plot holes than a mole infested farm, acting of the most mediocre caliber, the special effects barely scrape by and are rarely above syfy movie of the week standards, do we get any explanation whatsoever? (other than the squid thing) hell's no and the budget was apparently $13,000,000 (would love to know what the money went on? car rentals presumably).
For all these major flaws, I actually rather enjoyed it, I mean come on, you're never gonna watch a movie about a killer car and expect high art are you, but it was in my opinion, just good dumb fun, with some cool cars, just about everybody dies (although they're all such unsympathetic characters, this is surely a good thing) and as a drinking aid it works perfectly. Also it has an ending so open for sequel, you kinda have to give em credit for thinking that this movie would ever get a follow up, the tune over the credits is pretty sweet too.
So if this does ever get a sequel (seriously, seriously doubt it) count me in, I'm intrigued to see just how a shed load of giant squid aliens, disguised as cars will take over the world.