Overmatching filler metals has been a problem noted by several industry articles. Sorry, I don't have links to any of them but I strongly advise caution.

http://www.jflf.org/pdfs/papers/keyconcepts6.pdf
Above is a link to an article that talks about under matching, matching and over matching filler metals/ base metals. It gives a few design considerations to take into account when choosing your filler metal.
John Wright

PRCI (Pipeline Research Council International) has demonstrated the value of using weld metal with higher yield strength than the pipe, particularly with high strain applications, as long as reasonably good toughness is still present. Of course the higher susceptibility of higher strength cellulosic weld metal to hydrogen cracking needs to be considered when developing the welding procedure. Available reports can be listed by going to http://www.prci.org/publications/publications.htm
and using "matching" or similar criteria in the search box.

The article cited by jwright650 is good since it points out the difference between actual properties and minimum specified properties. Note, for example, that it is not uncommon to buy steel pipe with specified minimum yield strengths of 35, 42, 46, or 52 ksi (grade B, API 5LX42, X46, X52) that end up having actual measured yield strengths greater than 60 ksi. We have reviewed some test reports for heats of X42 pipe with yield strengths greater than 67 KSI.