Due to the recent amount of bugreports that are filed against KDevelop4, I’m inclined to write this.
When you find a build error in KDevPlatform or KDevelop and you can’t fix it yourself, write to the kdevelop-devel mailinglist. Subscription is here: http://www.kdevelop.org/index.html?filename=mailinglist.html
If you find crashes, other bugs or have feature wishes: Write to the -devel adress as well. KDevelop4 is not open for general testing, its currently in a kind of alpha state. So anybody trying to compile or run it should be able to either fix problems he encounters himself or talk to the developers on the mailinglist or on IRC (in #kdevelop).
Until further notice all bugreports against KDevelop4 will be closed as Invalid.