"We have much more faith that this will lead the Bank of Japan to print a lot more money," Issel said. "So the yen should continue to weaken. That we have confidence in. But there are economic headwinds, starting because you had a lot of pulled-forward demand in Japan. When that comes, you have a little bit of a cliff, so a bit more uncertainty on the equity side," he said, adding he prefers to play Japan via the currency.
(Read more: HSBC strategist: Am I the last person in the world underweight Japan?)
Even those who are still positive on Japanese stocks sound like distinctly fair-weather friends.
"Japan is not a bet for the long term," Stephen Sheung, head of investment strategy at SHK Private, told CNBC.
"What we see in Abenomics right now, we do not believe it's going to increase the competitiveness of Japan over the long term nor is it going to offer a lot of fundamental economic value," he said.
But he advises buying into Japan's market, while hedging the yen. "For 2014, the focus is the BOJ to increase its monetary stimulus," which will boost inflation expectations, he said.
(Read more: Gartman sees continued bull market in Japan)
"These are things that will help investors to reallocate their holdings of Japanese government bonds to the Japanese equities. And the BOJ stimulus will also support higher-than-average valuation levels of Japanese equities," he said.
But Sheung is limiting his commitment, only planning to stick with a long equities-short yen trade until the Nikkei hits his target of 18,000 and the U.S. dollar strengthens to as much as 112 yen.
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter