Here is what I have found (feel free to correct any mistakes):
DAT Destroyer 2007
- 186 organic chemistry questions
- 184 general chemistry questions
- 313 biology questions
- 153 quantitative reasoning questions
DAT Destroyer 2008
- 186 organic chemistry questions
- 189 general chemistry questions
- 324 biology questions
- 153 quantitative reasoning questions
DAT Destroyer 2009
- 210 organic chemistry questions
- 212 general chemistry questions
- 350 biology questions
- 153 quantitative reasoning questions
DAT Destroyer 2010
- 232 organic chemistry questions
- 242 general chemistry questions
- 377 biology questions
- 156 quantitative reasoning questions
So there are more problems in the latest editions, but the real question is, are the new problems just repeats of the originals (i.e. different versions of the same type of problem), or do they cover new material that the original DAT Destroyer completely missed?