I single hand the majority of the time, and agree with most of what's been said. However, I don't know that it's that important to have access to both port and starboard sides. My helm is on the starboard side, and that makes it very easy to lean out the door and see how close I am to the dock. As a result, I always dock to the starboard side. If I end up in a situation where I have a port-tie slip, I back in.
I rarely walk the port deck, and now better appreciate some of the asymmetric house designs. Also, I love driving from the flybridge, but have never tried docking from it.
I also mostly agree with the midship cleat. On my boat, I can usually get a line on within seconds of coming to a stop. I say mostly because I'm often docking in currents, and contrary to what you're taught, I find it much easier when single handing to dock with the current. Two reasons. First my boat backs to starboard so with correct rudder position and throttle I can get the stern in and quickly get the stern line on. With the stern line on I can then take my time. A midship line will keep me from drifting away, but in a current, the boat will rotate on that line making it difficult to get the aft line attached. So when docking with the current, I get the stern line on first and take my time with the rest as the current pulls the boat into the dock.
I'm not going to re-open the twins vs single debate. I will say that it is important to have the tools (bow thruster in my case) to dock more precisely. You want to be as close to the dock as possible so that you have more time to do what would normally be done by your crew. Also, I rarely try and use spring lines for maneuvering when single handing. It just seems like too many things could go wrong. Another case for having a boat with good low-speed maneuverability.