No one can be in this hobby for a long time without having a few regrets - usually about equipment bought and sold.
Getting rid of my Novice station. Even though I donated it to the Handi-Ham organization, I later regretted handing off my Novice Station, which comprised of a Drake 2NT transmitter, a Heathkit HR-1680 receiver and a Globe VFO. The good news is that I have acquired like pieces and have my Novice station back (with the exception of the Globe VFO).
Selling my Icom IC-730 - I did the modification to get the low power setting all the way down to 100 milliWatts. I sold this in order to buy an Icom IC-751A. This was back in the day when I got interested in AMTOR and PacTOR and the IC-730's T/R relay was just too slow to support these modes. My interest in them was fleeting, as it turned out. My interest in QRP has never faded.
Selling MY home built HW-8. To this day, I consider this my biggest faux pas; and I still don't know what possessed me to do this. This had to have been the biggest Ham Radio brain cramp that I've experienced in 43 years of being a Ham. Fortunately, Dave KD2FSI gifted me with a mint replacement that he found on eBay.
Not keeping my Heathkit SB-104A station, that again, I had built myself After a while, I was blinded by newer and shinier equipment, I sold these (rig, power supply/speaker, remote VFO, station monitor) to afford newer stuff. Sometimes I think I was part crow, being attracted to new shiny objects. This is a major regret.
Semi - regrets:
Selling my K1 and K2 - but alas, I would not have been able to acquire my KX3 without doing this. Unlike a lot Hams out there, I don't have deep pockets.
No - regrets:
Selling my IC-751A - great receiver for it's day, but selling it paved the way for buying Elecraft rigs.
Selling my amplifier - what the heck was I thinking ever buying one of those in the first place? My fascination with QRO faded more quickly that you can say "Jack Robinson". In it's defense, it did keep the shack warm.
Selling my Kenwood Twins. The T599A and R599A made up my General station when I upgraded all the way back in 1979. I sold these to afford the SB-104A.
I still wish I had every piece of Heathkit gear that I ever assembled (and it was a lot). At the time, I guess I thought Heathkit, as we knew it back then, would never bite the dust. Hindsight is always 20/20.
These days, I am content with my station as it exists. I have a KX3 along with the KXPA100 amplifier (which I have not turned on in years - in fact, I took it out of the line.) No aspersions to Elecraft, but I don't need or desire a K3s or a K4. After all this time, I guess I've learned to be content with what I have.
72 de Larry W2LJ
QRP - When you care to send the very least!