Here go some statistics about what has been done during the SoC 2007 program as regards ATF:
The repository weights at 293 revisions, 1,174 certificates (typically 4 per revision, but some revisions have more) and 221 files. This includes ATF, the patches to merge it into the NetBSD build tree and the website sources. (mtn db info will give you some more interesting details.)
The clean sources of ATF 0.1 (not counting the files generated by the GNU autotools) take 948Kb and are 20,607 lines long (wow!). This includes the source code, the manual pages, the tests and all other files included in the distribution.
The patches to merge ATF into NetBSD, according to diffstat, change 209 files, do 6,299 line insertions and 4,583 line deletions. Aside merging ATF into NetBSD, these changes also convert multiple existing regression tests to the new framework.
As regards the time I have spent on it... I don't know, but it has been a lot. It should have been more as I had to postpone the start of coding some weeks due to university work, but I think the results are quite successful and according to the expectations. I have been able to cover all the requirements listed in the NetBSD-SoC project page and done some work on the would-be-nice ones.
I am eager to see the results of the other NetBSD-SoC 2007 projects as there was very interesting stuff in them :-)