Plenty of crossword puzzles are based on letter addition, and not all of them absolutely need a "revealer" to tie the idea together. But I think the best "add some letters" puzzles are those with some rationale; some raison d'etre. So I really liked MAKE IT LAST, interpreted as "add IT to the ends of normal phrases."

My favorite was SWING BAND to SWING BANDIT, as the meaning of that last word changed so dramatically. Generally amusing results overall, with some funny imagery of a Hormel spokesperson saying YES, WE CAN IT! SHORT STOP IT interpreted as a terse command to cease and desist also gave me a chuckle.
Some fun changes of meaning, i.e. CAN going from "able to" to "put into a can." I did wish there were more like SWING BANDIT, where the last word became a new word, though. CAN IT, STOP IT, POST IT … BANDIT. Would have been nice to have two of each, rather than BANDIT sticking out as different.
I didn't know LEGS DIAMOND off the top of my head, but what a cool name! Along with the clue referencing Dutch Schultz, I felt compelled to go read up on those two. IRS AUDITORS made for another nice piece of long fill. Along with SOAKS IN a HOT TUB, some nice bonuses. And it's not often that I notice a five-letter entry — in a good way, that is — but I liked the colloquial MERCH(andise).
The 11-letter central themer is so tough to work with. Ned uses one of the three main methods of gridworking around it, leaving himself big corners in the upper right and lower left. The former came out so well — beautifully smooth, if not snazzy. The latter demonstrates the trade-offs seen more often in these types of corners, with the esoteric ELOI, the APA, and BE A HERO sounding a little off without DON'T preceding it. But without much else in the grid standing out — just a bit of ANO / INT — it's generally well-executed.
It might strike some as odd that such a little 3x3 section would require both ANO and INT, but those little chunks can be devious. 4x3s or even 4x4s can often be easier to fill, what with more "good" four-letter words than three-letter ones.
Finally, really nice to get a clever clue right at the start: [One may bug you] isn't a pest, but someone might place a listening device — a SPY. The clue looks so innocent … just like a SPY!