I've had 2 IQ Tour Solids - one pin down, and one pin up. I still have the pin up one.
I had some success with the pin down one - winning a USBC Masters qualifier with it. However, other than that, nothing. I could never really get the ball to transition from hook to roll quick enough to feel comfortable with it on almost all conditions - most of the time it would just plaque when it would get to the pocket. The pin-up, with the quicker response layout, has been much more versatile for me. While it's been better, there are better options for my style of bowling on most of the conditions that I encounter on the left side.
Ultimately, what I have learned from the IQ Tour Solid (and the Gold Ball/IQ Nano/UpRoar) is that low diff balls seem to be condition specific for me. They work best for me when the back ends are SCREAMING. These balls don't peel off the spot for me, so there is a place for them, just not that often.