I'm definitely one of the "slow learners" but I've finally gotten to where I can ride down the street on my S40, turn around and come back, rinse repeat. A couple of my learnings which might help others:
I was having a LOT of trouble turning. I went back over the "How to learn to ride" instructions and watched several videos, and I realized I'd skipped the step of doing figure 8s while Flinstone walking the bike. 20 minutes of Flinstone 8s and my turning improved, but it was still terrible. Then I figured 2 things that helped me improve more:
1. Sit up straight when you turn
Ultimately I'd like to get to where I can turn just fine laying back, but I'm not there yet. As an interim step, sitting up straight where my chest almost touches the handlebars changes the dynamic of the bike and makes turning much easier. I can't hammer this one in enough - for new riders struggling with turns, try sitting up before you turn.
2. Remember you're on a short wheelbase bicycle
This one is a little harder to describe, but I realized that I was turning as if the wheel was where the pedals were. In my head, that was the length of the bike, so it made sense to steer when the pedals were where I wanted to turn. So much of the instructions are focused on the dynamics of the MBB and its effect on turning, it's easy to forget that the shorter wheelbase is also a factor. I started thinking as if the front wheel were directly below my butt and turned accordingly. This was a MASSIVE improvement.
I was also having trouble understanding the "Lean out while you turn" instructions. It seems like all the videos of cruzbikes show them going in a straight line. Robert has some great videos where he turns, but Robert is a zen master on a cruzbike, and his leans are a bit too subtle for me to pick up on.
I did some research on motorcycle forums, and I think I found the term people are talking about: Counterleaning. Here's a great video on counterleaning and how it fits into a motorcycle's dynamics: