I tried an LA4 and I didn't keep it long. It wasn't so much as neutral as it was forward and fatiguing. I'm sure someone will chime in with the old adage that it was just showing me the true nature of my system. But a Hattor Audio "The Big" preamp, which is what I currently use, is much more enjoyable. And since it's purely passive, there is nothing to color the sound or "enhance" it. It just sounds better to me.
So if you like the LA4, you are probably in the majority. It just didn't work for me.