6.10.4 is extremely old (especially, according to haskell specifics).Realizing after compile error, that Data.Functor (for example) was not always there, is very confusing.The most recent stable version is 7.4.1.
Seconded, this means a lot.
It's also gotten much better at optimization, which can make some programs run several times as quickly with the new version as with the old.
It would be great if GHC is update to 7.4.1.
By the way, if anyone reads this who can do something, please don't just install GHC--please install the whole "Haskell Platform". Several key libraries (such as System.Random) have been moved out of the GHC base.
Yes, please update GHC and install the Haskell Platform. Haskell users can't really compete with other languages because of the compiler is so old.