We purchased the personal cups+adapter three months ago and we use it daily for morning shakes. It works well, it is very high quality and it is dishwasher-safe.

I am a trained kitchen professional and I use vitamix both for my catering business and my home cooking. I had originally thought this was a frivolous (why not just use the usual blender container, etc.) purchase but the convenience of (clean-up, small size) it is so great that all my concerns vanished once we incorporated it into our daily routine. 

It is a bit pricey but if the convenience is important to you, it is worth it.