I can honestly say that in over 600 transactions, I have only had 2 bad ones, and both were small amounts, and were eventually resolved. Without eBay, I would have never been able to get parts for my antique Packard. I also would have paid excessive prices for other parts and supplies that I have bought over the years.
Examples: 1) Replacement motor for my dryer - retails locally for over $200. Found on eBay from a retiring dealer that was liquidating his business for $60 with free shipping.
2) Ignition module for weedwhacker. Locally more than the machine was worth. eBay for $12.00
3) Taillight for pickup. Locally $175 from dealer. Aftermarket on eBay for $35.
I could keep going with many more examples, but I think you get the idea. I **LOVE** eBay!!!!
Now consider: out of millions of transactions daily, only a handful turn out badly. In your case, slow shipping, poor communication, and attitude are his transgressions. Give him the negative feedback if you must, but at least be truthful and objective. That will most likely hurt him more than venting here.