I only have Jovan (the price was irresistible), but I'm very interested in trying Kiehl's as well.
As for Jovan, the first several minutes following application are off-putting, with a strong synthetic-y, alcoholic vapor plume. Once that stuff boils off however, it's rather pleasant. I'm not a layering kind of fellow, but if I were, Jovan might be useful in laying down a simple musk base to a fragrance lacking that note.
There are lots of others on this board who can weigh in on the relative strengths and weaknesses of both Kiehl's and Jovan.