I was surprised that critics disliked this one for I enjoyed it much. I found much of the humor great, and I found the performance of Robin Williams wonderful. The romance however was not done very well, mainly because the character of Laura Linney, herself a very excellent actress (remember Kinsey), is very annoying.
Those critics mentioned dislike of mixing the whole thing with conspiracy, and in hindsight, it was quite unwarranted. The movie would have done fine without it, and it was just not done right, and Jeff Goldblum performance didn't help either.