I think that using two arguments is better than the dots:
'%+%' <- function(x,y) paste(x,y,sep="")
"a"%+%"b"%+%"C"
[1] "abC"
If you really really want to you can overwrite +, but be veeeeery careful when doing this as you will break one of the most important functions in R. I can't think of any reason why you would want to do that over %+%:
# '+' <- function(x,y) paste(x,y,sep="")
# "a"+"b"+"C"
# [1] "abC"
rm('+')
commented it out to be sure I don't accidently break someones R:)
