You're gonna find two opposing camps for this machine (or any T&S)- those that love them and those that hate them. I have a 630 that has sat in a corner for 5 years, I've never touched it. Someday I'll get it unburied and play with it. The biggest concern is the gears are now old enough to crumble if they haven't already. There are replacements available though. Fiddly bits are common and always available on all the major sites.(Ebay, Etsy, Shopgoodwill, etc..) Another thing that you should be aware of is the foot controller is specific to this model and the 640 only.
Cari