The first time I saw a Gates Sta-Level was in a session with producer Jimmy Boyle. It was stout and military in style, and had a soft yet firm grasp on the vocal he was mixing. I was impressed. He had other unusual broadcast limiters and compressors, such as RCA BA-6A, Collins 26-U and Gates SA-39b. This was around 1993.
I immediately started cold-calling radio stations on the hunt for these units and found them relatively plentiful and inexpensive. This was at a time when radio in the United States was changing from analog to a digital, so the old broadcast tube compressors were sitting on dusty shelves in the back rooms of the stations, ripe for the picking. I took the opportunity to buy as many broadcast compressors as I could find, keeping the best units and selling off the surplus to my studio buddies. I found fantastic vintage gear by CBS, Collins, Spot-Master, Gates, Innovonics, RCA, Electrodyne, GE, Federal, Harris and Western Electric.
Over the last few decades I've had a chance to really get to know the personality of each brand of these vintage compressors and what they are good for. I find the Gates Sta-Levels are the most versatile, they are excellent on vocals, bass, drum room, acoustic guitar. They are not too wild but you can push them hard for effect. Unfortunately the old Sta-Levels will periodically need maintenance, and if you blow a 6386 tube, it is costly. The Retro re-issue Sta-Level is a great alternative to the vintage Gates unit. I have put them side-by-side and find them very similar, with the Retro more steady and stable than the old Gates. If you're holding out on not buying a re-issue in the hopes of finding a vintage unit I would tell you not to wait. The re-issue units will get you 98% of the way home.
Sta-Levels are definitely on my "must-haves" list. Here are other items I can't live without:
Universal Audio 175b
Empirical Labs Distressor
Aengus graphic EQs (500 series)
Oh yeah, and I "must-have" a Neve 8038 with 1073 mic pre/EQs