This film makes no pretense about being anything except a fairty-tale fantasy about time travel. You can see it in the visual language of the film, Japanimation translated into live action complete with all the camera moves, larger than life characters and primary color scheme. If you have a chance to see it in a theatre, as I did, go.
Slipstream's not about the real world but an alternative universe where time lost can be time regained and all your past mistakes erased. But it's not Primer and it's not meant to be. It's not exactly a spoof either -- more of a celebration parody of the sci fi action genre.
While it's ninety odd minutes of fast-paced entertainment on the one hand it doesn't take a genius to detect something else at work here, beneath the surface, a straight to video title actually intended for the initiated, the film literate. Note the Sergio Leone style soundtrack during the bank robbery. The glint in the actors' eyes when they deliver their lines. Vinny Jones' performance says it all, deliberately cockney and spoofing the Lock, Stock persona to perfection. And Astin's not far behind -- anyone notice the line on the plane when they're all about to go to hell in a handbasket? "Oh, yeah.. the plane's about to crash so I better do something!". If you don't get it by then you really weren't watching.
Read between the lines and you'll begin to see that this is a film about the sci-fi genre and about action films in general. If you don't get that, you've missed the point. Restart the DVD and watch it again. And maybe you'll really enjoy it this time. Don't be fooled, this is imaginative stuff and not your run of the mill heavy TV scifi. The last thing Slipstream does is take itself seriously. And that's a delight, at least to this reviewer who, along with three hundred other people in the same theater, was gobsmacked by this unexpected display of ingenuity.