OK, so I've been procrastinating for a few years. My son bought me a clutch "Unlock Valve" from Bavarian Autosport (their part number is UNLOCK2) for my 2004 E46 330i. I put it in today. Wow! All of a sudden, I can shift smoothly without thought or effort. The difference really is pronounced. I should have done this literally years ago, and I can't believe BMW put the stupid thing in to begin with.
Then, I drilled out my old lock valve (aka clutch delay valve, BMW part number 21526755892) and put it in my wife's car. It's actually a bit more complicated than that. It takes a while to get all the stuff out while leaving the important bits of the fitting intact. But with a drill press, a small punch, a pick, brake cleaner, and patience, it was not hard, and took about 15 minutes overall.
My wife is *very* happy with how her E46 325i shifts now. A productive afternoon...