I've used a plastic Henge Dock with my MBA for the last 2.5 years without any issues. Just plug it in, attach the power cable, and hit a key on my BT keyboard/trackpad and go.
The ports getting worn out is an interesting topic. The prongs on the USB port which gets inserted into the dock on my MBA are definitely a little more worn than the one on the other side of the laptop. However, I've never had an issue with plugging any devices into the port. Realistically I've probably plugged more USB devices into the port than the dock, I use it to charge my phone all the time when at home. The Thunderbolt port doesn't look any different and I've never had any issues with it.
The nice thing about this one is the power cable is built in on the bottom, with the MBA the power was on top so you still had to plug it in and have a cable hanging around.
They are very stable, you aren't going to knock it over without some force... Pulling the device back out you need to press onto the base of the dock, but I don't even know I'm doing it anymore, it's just second nature.