I have had three of these now in around 15 years.  Yes I said 15 years, or at least since they first came out.  They are the best trackball that was ever made,ever made.  They fit your hand like no other trackball out there including any that Logitech has made since.  I really hope that Logitech will make them again, because you can't beat them.  They are so expensive now that most of the time you can't find one that you can afford.  The few that are out there that are new are being sold for close to $500.  That is just unheard of.  Of course those doing that probably won't sell it or maybe they might.  Used ones are usually REALLY USED and the buttons will go out sooner or later.  But if you can find one that has the Logitech logo intact on the top and hasn't been rubbed off, then it wasn't used much because that is the first thing to go and it doesn't take long for that to go, maybe about a year or less of use. The one I have just purchased, the logo is sharp and so I know that it hasn't been used much. Even this one wasn't cheap, but it was cheap enough that I was willing to foot the bill for it because you can't beat this trackball.