I never got the Arms Micron Rumble or Frenzy, which I think are the better versions, but I've had the RiD version. "Not impressed" was too strong a phrase to describe my opinion of it, and I apologise. To me, the figure was just ok. No hard feelings to fans of that mold. While I didn't think it was bad, it just struck me as a bit generic. If it didn't have to compete against Deluxe RiD Vehicon or Arcee, it would have been a top tier (in my eyes).
I like G1 Rumble, and I like how the side doors simulate G1 Rumble's wings/guns in robot mode. But the car-roof-kibble on the arms stand out. Normally some car kibble is acceptable, but the Vehicon hid its car kibble so well that it beats out the Rumble mold (in my eyes).
Also, and I think this due to my bias against hatchbacks combined with the Geewun fan in me (cassette not hatchbakk); I just found the alt-mode very plain. It looked like just another car, and I already have so many car Transformers...
Prime Rumble/Frenzy mold isn't bad, it just didn't grab my attention.
I like to treat my Transformers collecting as an escape from reality, which is why I'm quite fond of fantasy alt-modes like spaceships, futuristic tanks, and mechanical beasts; provided that they look tasteful and the robot can pull off the look without cheating (shell-forming, parts-forming etc). I also like diversity in my Transformers, and to me the Earth Car alt-mode is very common.
It's even gotten to a stage where, unless it's a character close to my heart (like G1 Mirage or Chromedome), I'd pass any new transformer that becomes a car. I don't even have any of the CW Stunticons.
But please, don't let my remarks dampen any love you might have for car-Transformers. They're great figures, but for me, I've got plenty of good car-Transformers and would like something different... Like a Triple-Changer that transforms from Robot to Mechanical Space Griffin, to Drill Tank and back! But well done of course.