Just a comment, there are thousands of excellent Chinese papers written in journals which never get translated to english. Being able to read both is definitely good if you are willing to put work into researching.
[EDIT: Douglas S. Stones] I've been learning Chinese for roughly three-and-a-half years now and I feel it has been given an unfair treatment so far in this question. So I will add a few reasons why I found learning Chinese has been valuable as an early mathematician.
a. There are many talented Chinese researchers that are looking for international collaborations (here's my first: http://portal.acm.org/citation.cfm?id=1734895).
b. Merely restating a result (that has been published only in Chinese) adds something to a paper that others can't easily match.
c. I can pronounce Chinese names at conferences without sounding like a goose to the Chinese speakers in the audience (e.g. "Wang"). These are some of the most common surnames on the planet.
d. In learning Chinese, you make your knowledge work for you -- you actively find papers in Chinese, etc.
e. There was an argument about traditional vs. simplified Chinese, i.e. not being standardised. It's pretty easy to switch between traditional and simplified (and pinyin) on a computer (I admit this becomes more complicated if you only have a hard copy or a scanned copy, but there are ways such as OCR or simply drawing the unknown character into appropriate software). For many characters, the traditional and simplified characters are quite similar. [Side note: If I redefined "English", "German", etc. to be "European language 1", "European language 2", etc. then "European" would not be standardised. Why would you want to learn "European language n"?]
f. There are native Chinese speakers everywhere!
That being said, learning Chinese (as with any language) requires a certain temperament and a long-term commitment. But it is easier now than it has ever been in the past thanks to online learning tools. My favourites are ChinesePod, Skritter, dict.cn, DimSum Chinese Reading Assistant (but there are plenty of others).