Dont quote me on this but IIRC he has actually gone out of business. The ebay seller does not make them. I think he is just selling the leftovers. Ive had a few conversations with him regarding the possibility of replacement parts. I had read somewhere that the Roberts "guy" was actually sued...
Hydraulic and price. Can usually be had for $125 or less. Hydraulic is the only way to go, ive had the mechanical Mitchell and it worked, but hydraulic is so much easier, especially with the more stubborn heads.
This is the scale I have as well. As far as tip weights go I use these: http://www.mitchellgolf.com/Brass-Tip-Weight-Kit-For-Steel-Shafts-144-Pieces.html because they are reusable which is nice if you do tinker. Also for lead tape use this: http://www.golfworks.com/product.asp_Q_pn_E_HDLT the...
There are a couple calculators online that can get you close but I dont trust them fully. You can pick up a scale for less than $50 and I use mine all the time. The process is quite simple. I dry build the club and put it on the scale and then determine if I want to use tip weights or lead tape...
I use the roberts shaft puller. Best money in repair tools, i use it to do grips as well. Ive been looking for a loft/lie machine but I only trust Mitchell and they arent cheap.