Another +1 for the Flex 3401 VRG polisher here. I just bought mine a few weeks ago after using a Porter Cable 7424XP for a few years and the difference between the two is crazy. So happy with the Flex and the power it has to cut through almost anything. You won't be disappointed with it at all.
The only thing that it can't do that leaves it lacking slightly is have 4" pads on it. Would definitely be nice to have that ability for smaller areas. I can see myself buying a second polisher to throw 4" pads on to get in those areas in the future.
The truck definitely came out great! I've been using Adam's products for almost a year now and am beyond impressed with every one of them that I've used. Fantastic quality and like you said, are all made to work together which is a bonus as well.
The 12 hours sounds bang on the money for the work you had done; that's right at what I would have estimated it at as well.
To show you what the power of the Flex can do here's the recent project I just used it on.
I bought this '65 Nova about a year ago. The previous owner was an idiot in more ways than one that I won't get into, but one of the things he did was sand down all the paint on the body. I have a feeling it was trying to wet said just without the wet and it came out horrible. Here's what it looked like when I brought it home:
I polished it up a bit last year with my Porter Cable polisher and Meguiars Heavy Cut Polish to at least get it a little better but it was still nowhere close to where I wanted it. So after doing a bunch of mechanical and interior work on it this year it was time to finish the polishing job. I ended up wet sanding the front end and trunk lid as they were never done and then polished it up from there. Here's what I ended up with.
As you can see it almost looks like a whole different car. Or that it was painted at least. Here's comparison of what I had done last year with the Porter Cable VS this year with the Flex.
So to reaffirm your decision, the Flex is definitely the way to go IMO.