"Does it blend better without needing to use the tamper?"
YES! I make "Jamba Juices" every day with 90% frozen fruit, I am amazed that either the 'presets', 'wider container' or 'different motor' finishes our smoothies with no assistance from me. And about the tamper, that would be my only complaint, it is now made from the same material as a toddler's baseball bat made for plastic nerf balls ( http://goo.gl/M0KKX ). However, the tamper serves its purpose--when and if needed.
"Do you think the 750 is worth the extra money over a refurbed 5200?"
I returned my 5200 for a 750, there is hardly a comparison between the two--for me. It is quieter, but I don't think it is a 'night and day' difference. I now blend with the presets and originally thought that they would be unnecessary or useless. As it turns out, since I am not needing to babysit with the tamper I love doing other things knowing that it will turn itself off.
The bottom line: for what I do (smoothies and soups) my 5000 works great and the 750 is just a really nice upgrade. Best wishes!
I had my 5000 since 1999 and picked up my 5200 about two months ago. After seeing the 750 series at WS a few days ago, I started my research. After reading this post I decided to go pick up a 750.
Simply put, I really liked and used my 5000 for 12+ years, I loved my 5200 for two months, and I am blown away by this 750 after one meal.