Love my Thermy, had it for about 5 years and it hasn't missed a beat.
We use it everyday.. Made the best Butter Chicken in it last week..
We make butter, cook rice, steam puddings and veges and anything else you want to stream.. Mashed potato, sorbet.. Prosciutto wrapped chicken is amazing all while cooking the sauce in the bottom at the same time.
Powerful enough to crush ice, unlike a blender...
The main difference between the thermo and a cheaper alternative is the reverse function, and the blades.
Using reverse while cooking stops food being mushed up too much, and the food in the cheaper models have a tenancy to get stuck under the blades and burn.
I don't sell them, but I wish I had commission on the sales that's have occurred due to my raving about it ;-)
My advice would be, if you bought one second hand, you should organise a demo, they will be happy to do that, other wise go into the thermomix forum for receipes. They are step by step easy..