I have had a lot of experience using web 2.0 properties for linkwheels, and indexing seems totally random to me. For example, I would normally say that Xanga takes weeks to get indexed and not recommend it, but on my last linkwheel it was indexed in fifteen minutes.
However, I have noticed that the real web 2.0 / blogging players seem to be: wordpress.com, blogger.com, hubpages and squidoo. These four properties have tended to be indexed first and rank best for me, on average (over the course of about 20 linkwheels). Outside of these four, all I can say is that it seems random and depends on what you do, or luck.