Thank you jack for your replies.
In my experience it varies a bit more, and usually the result is not quite neutral to my eyes. Most of the times I find it a bit red. Evidently, I would not use any neutral result as is in most of the cases, especially not when I do portraits, which is what we do here. But I like to have a visual reference.
As I did not get so many answers, I reposted this question in the equipment section of the LL-forum (http://www.luminous-landscape.com/forum/index.php?topic=47189.0
). Bart van der Wolf suggested BabelColor's white target to me. I'm very pleased by the results I got after the first day. What a difference!