SyncEvolution + non-recursive Automake
Krzesimir Nowak wrote about his work on converting SyncEvolution from an autotools project with recursive make to non-recursive make. Definitely worth a read for anyone interested in autotools. The current SyncEvolution master branch (post 1.2) uses that new build system.
His conclusion is that the new system is not necessarily easier to understand than the one before (autotools with some preprocessing shell scripts). Partly that's because SyncEvolution tries to achieve certain things not supported well by autotools (automatically generated version number, avoid listing all files explicitly, backends which can add to the global configure script), partly it is because non-recursive Automake introduces additional constraints (like having to avoid clobbering variables and rules). Helper scripts are still needed, the only difference is how they get called.
Either way, what sold me on the idea of a non-recursive make is that on a machine with many cores, like the SyncEvolution nightly test server, compilation is considerably faster because parallel make can spawn more jobs in parallel. Recursive make often had to wait for the completion of compilation in a sub-directory. If memory serves me right, it was more than twice as fast.