If you look at the vDyno, he's at ~20psi at 3500rpm. Starting to spool at 4krpm is super laggy, especially with a smaller turbo. It comes down to a few things - the install, the parts, and the tuner. As for [MENTION=1568]wspec[/MENTION] car I'd say he starts to feel the pull at ~2.8krpm. By comparison, with my 2867r the fun starts around 3k and is @20psi by 3800 and usually I'm rocking full spool (28-29psi) by 4krpm. DHM is SUPREME.
Viva la [MENTION=1098]DHM[/MENTION].
Anyway, datalogs can tell you what it's like without actually experiencing it. What I mean is this: I took a look at my stock turbo, Cyborg and 2867r datalogs to look for a difference in elapsed time between given speeds. This was a while ago, and I don't have the data available at this moment so I can't be 100% accurate, but there was really only tenths of a difference in speeds from about 20mph up to 50mph or so. The difference being that the big turbo was slower...by tenths. I went up against another member at the track who is tuned on E40 and that 1/4-mile slip (that's in the 1/4 times thread) corroborates that data.
That brings me back to what I first said. Spooling a big turbo is going to depend on a few things - the parts, the install, and the tuner. It'll spool fast with the right parts and the right tuner, as long as it's installed right...barring other issues.
Edit- My last datalog I saw 20psi @ 3213rpm and 29psi @ 3490rpm. It's turbo weather here in Illinois.