I had nearly forgotten about the ISP-6, which was really great. Sure, it looks like the cheapo one man version of the Lambda class Imperial Shuttle, but as a kid I had two of them, both with the top canopy broken off (got them at garage sales), without the top wing (which is connected to the canopy) they simply look like generic star fighters. I think most of us could only afford one X-Wing as kid, so the ISP-6s made great wing men for my X-Wing, padding out my Rebel squadron a bit. Alternatively, I could pop a Stormtrooper into each ISP-6 and have something for my X-Wing to shoot at (since I never owned a Tie-Fighter) with its nifty buzzing noise and francy flashing red light. For a kid who made many of his own ships out of toilet paper roll tubes, paper cups, and tin foil, the ISPs were pretty sharp looking.
I think Kenner was very wise in making the mini rigs as budget ships for kids who didn't have a lot to spend on toys. After all, what was Star Wars without spaceships? And a lot of the movie ships, like the Falcon, the X-Wing, the Tie-Fighter, and many of the others that followed were pretty big investments for some parents.