To start, I called to make reservations as my voucher said to. They told me I needed at least 6 people to make reservations, I only had 4. So I rounded up 2 more people, bought 2 more vouchers and called back. This time I was told I couldn't make reservations if I had a voucher.
Once we arrived, signed waivers and bought their helmet socks we were told there were going to be 3 groups ahead of us (the exact reason why I was trying to make reservations was to avoid waiting for a long time). Turns out there were 4 groups we had to wait for at ~10mins each group, plus loading and unloading. This was frustrating.
Overall they were a blast to drive but not one of the karts was even to another. The first one I got ran great and was fast, the second 2 were slugs compared to the first.
The employees didn't care if you bumped, which was a bit annoying. My wife got bumped numerous times and ended up with a sore back after 2 of the 3 sessions. Nothing was said to the other people on the track that kept bumping and spinning people out.
If you can get a group big enough to prevent people you don't know being thrown in with your run group it would be best. That way you don't end up with some wreckless punks ruining your good time.