I have sold and traded many over the last 10 years. I miss some of them a little but not too bad. I have been slowly improving the quality of my collection. When I first got into shooting, and was on a tight budget, I wanted the most bang for the buck I could get. Now I appreciate the finer arms. One well placed shot is better than 100 sprayed all over the target.
I have traded/sold a Colt Defender, Romanian Tokarev, A Taurus TCP, A Yugo SKS(I liked it, but had other SKSs) A Romanian PSL, A Draco AK pistol, A WASR 10, A Ruger 10-22, a Remington 870 and 1100, a GSG 522, an RG22 revolver, A CZ-72, A Remington 700, a Taurus 1911... and maybe a couple others I'm forgetting. I don't overly miss any of them. Some I traded to other guns, sometimes I needed some cash. But I moved on to better things.
None of them were real lemons. The biggest let down was probably the PSL. I lusted over it for months, saving up every dollar I had to buy it. Shooting it was just not pleasant... it wasn't accurate enough to enjoy, cleaning it after corrosive ammo was a pain, the acrid corrosive ammo smoke blown back into your face after every shot was bad too. The stock was too short, the trigger was bad. Neat guns, but just not for me.
Overall though, I don't regret any of them moving on. I'm happy with my collection now.