I fully agree with a lot of the criticism about copyright assignment - it adds beaurocracy, suit involvement, and all that. However, aside from that additional overhead, it isn't intrinsically evil - which can easily be seen from the fact that projects with copyright assignment can be forked into ones without such assignment. In other words, it allows those that do not like copyright assignment to always get to where they want to be.
And this is the part of the criciticm of copyright assignment that I don't get. If we really believe in our FOSS licenses - and we should, otherwise why use them - then they will preseve our freedoms in both copyright assignment projects or in non-copyright assignment projects. To say that there is something non-free or evil or wrong about copyright assignment projects, seems to imply that our FOSS licenses are deficient, if they cannot guarantee our freedoms.
But, they can and they do, as we can see from the possibility of forks, and examples of them.
Again, I don't care for copyright assignment myself - it just adds overhead. But I wouldn't stop myself from contributing to a project that does have it, or prefer one project over another because of it. It doesn't matter to me, as long as both projects use an open source license. That's the important part, not copyright assignment.
The only real difference with copyright assignment is that it allows the person getting the copyrights to offer *additional* licenses. Typically this is used to offer commercial/nonfree licenses, like Qt and MySQL do. I see no problem with a company making money in this way. It seems though that a lot of the anti-copyright assignment criticism stems from a distaste of such things. But making money is not antithetical to FOSS, in this context (as often mentioned, you can sell GPL software, odd as it sounds to people that are new to FOSS).
OTOH I do see a big advantage in being able to change FOSS licenses later on. If the vast majority of a community would like to change the FOSS license their project uses, they should be able to (it should take a special majority - just like changing the constitution of a country requires a special majority). Copyright assignment makes that possible. But again, this isn't a big enough of a deal that I would prefer copyright assignment over the lack of it.