I've only infrequently regretted the decision to get rid of stuff.
But never regretted it enough to go and buy the item again :)
For example, I decluttered lots of books when we shifted house 10 years ago. At that stage, homeschooling wasn't even on the horizon, so I got rid of a few reference books that were just huge and taking up valuable shipping space. Turns out one of those books (a gift from a grandparent) would be GREAT to have now, and expensive to buy. But such is life.
And the occasional music CD that I sold has, some years later, found me searching the shelf looking for it, and muttering "I KNOW I had this CD", before remembering what I did with it. Again, not a big deal, and if I really want it, I can go get it. Turns out I don't want it all that badly after all.
But for technology - definitely sell it while it still has some value. It will be obsolete within 2 - 5 years anyway, so it's not at all in the same league as antique family items.