To buy or not to buy a used cartridge?

I have mixed feelings about this also.

I agree that this is probably the one item that I would consider being a risky purchase, if buying used. There is just so much that can go wrong buying a used cartridge.

However, that being said, I have bought three used cartridges:
A Dynavector XV-1S from a friend, (okay, that was a pretty much a safe bet),
One from a guy on Audiogon, (A Shelter 90X, which was in very good shape),
And even one from a guy on Ebay, (which while it did make me nervous, the Koetsu Rosewood Signature was in near mint shape). So, all things considered, it was a great way to save money. (I bought these for about 30-35% list price.)

If you deal with a person who you feel comfortable with, (especially if you've spoken to them, or if they post a lot here or on Audio Asylum), then you can probably get a decent deal. Buying from an unknown entity is likely to make for an anxious buying experience, but not necessarily a bad one.

My two cents worth.

I have brought 3 used cartridges and have not had a problem. All have come from audiogon and have been from people that frequently post. Not sure that is a guarantee but most on this site are into the music and gear and not about screwing the uninformed or novice buyers. If you go to ebay or others, good luck. that imo would be a crapshoot as there are a lot of unreliable sellers on ebay

I have bought literally dozens of used cartridges, and while it is an extreme risk because half are no good, the price is right, and often there are treasures that compensate for money wasted on the others. All you need to know is that you will get stuck half the time. To me, that rare jewel is worth the risk, though.

I am 100% in accord with Mosin. If you purchase lots/dozens of vintage carts, you can expect some to disappoint, either with cantilever or suspension. On the other hand, you can find some great carts for not huge money, and those which are 'damaged' in some way can be repaired.

I just recently picked up a Sony XL-88 for which I have high hopes. My other example of that cart is a real treat - one of the nicest combinations of delicacy and richness around. Those haven't been made for more than 25 years. I have purchased several XL-55Pros of a similar age and have had pretty good luck, only happening on 2 'baddies' among several. Likewise with older MMs - only one 'bad' F-8 (cantilever bent). I have purchased a Koetsu Rosewood Signature which was really nice, and a Victor L1000 which has been a pleasant surprise.

If you purchase recently-made (last several/ten years) high-end carts from people who take care of them, the biggest worry is how they are packed/shipped.

I was recently wondering whether it doesn't make sense to weigh carts down slightly inside the packaging just to make sure that the padding around the cart acts better as a dampener. Carts are so light they could bounced around easily.

locally only. let me play it first, pay second and than unmount and take home.