I'm not going to cop out and say it depends (though what methodology you use matters). I'm just going to come right out and say that it looks slightly undervalued overall.
This headline "S&P 500 Profits Cut First Time in Year by Analysts" should give some pause because I don't like it when earnings upgrades give way to downgrades while the market is struggling to make gains. That generally signals some warning signs. However, there is a fair amount of cushion regarding earnings estimates. The article states that S&P 500 earnings estimates were cut from $96 to $95 for the S&P 500. That's based on a "share" of the S&P 500 if you view the index level as a price. So then, the basic calculation is made with the S&P 500 trading at 1165 and earnings at $95 the S&P 500's PE ratio is a whopping 12.26x. Not exactly a historic high. As such, estimates could be cut a great deal and the market still would be in decent condition from a valuation perspective.
An annoying post from Mish's Global Economic Trend Analysis references the 1970s where, as market historians know, the stock market failed to advance throughout the decade. The S&P 500's PE ratio entered the decade at around 16x and left at under 7x, representing severe multiple contraction. However, if you look at long term interest rates, as we have in previous posts comparing the relative attractiveness of bonds to stocks, this makes sense. 10-year treasury rates rose from around 7% to as much as 12.75% by March of 1980 (the same month cited in that post) and then up to a high of over 15% by 1981. If you look at the comparative earnings yields and interest rates, you have stocks at 6% or so at the start of the decade with 7% on treasuries. In 1980 you have stocks at 14% (approximately) and bonds at nearly 13%. I rounded a fair amount here because I am feeling lazy, but the post I'm responding to was even lazier.
Currently, by the same comparison, stocks at a forward earnings yield of 8.15% (not the same comparison, but let's use it for now) and the ten year treasury is at 2.39%. Depending on your metric, you might use the ten year trailing PE ratio, which puts us at 21x earnings, or the one year trailing which seems to be more like 15x (depending on what is included in trailing earnings). In any case, unless interest rates start rising a great deal, which is highly unlikely, the outlook for stocks is fairly constructive at the moment.
Edit: I just remembered that we had an earlier discussion about whether or not the spread between earnings yield and interest rates is a good predictor of future returns. Generally it isn't, but the relevant comparison is whether or not it is useful for selecting between stocks and bonds which offers the best return and on that count it performs reasonably well.