This market has had a huge run and if I were flexible, at the margin I'd take some off the table. That being said, I still like this tape and think it will be higher 6 months from now.
The bears will tell you that either stocks are not that cheap, or are expensive. My contention is that it is impossible to know.
If you own stocks, or are contemplating buying here, what you care about is future fundamental performance relative to current expectations. Since I believe that the economy is recovering, I am willing to bet that earnings will be much higher than current estimates at some point in the future, and probably next year. If you are only willing to use current earnings, trailing earnings or current estimates, you are putting huge faith in things not changing, or that the sell side has the correct estimates for the next few quarters or years. Good luck with that.
I'm cautious short term (next month or so depending on levels), still bullish longer term.