Bret-
We're both looking for the same performance out of our interior products. I used to dislike using anything on the vinyl except some mild soap and water.
Then, a friend recommended Vinylex. Since I had used Lexol, I tried it - and liked it quite a bit, except for the sheen left on the material, despite all the buffing I tried, couldn't get it out.
303 was something I actually had for my boat, didn't even think of using on the car (and honestly, wasn't that impressed on the boat - then again, that was severely weathered vinyl, exposed to all the worst elements all the time).
In the car - it is EXCELLENT. After application, it's like you never put anything on! Matte finish, almost allergic to dust! Like brand new vinyl.
I say go for some - considering you can pick it up locally, and it's relatively cheap (8 oz at least) it's worth a shot.