It's been reported that some of the content of the Steele dossier has been confirmed correct by the FBI. But i don't know specifically which aspects. On the other hand there are, so far as I am aware, no parts that have been proven false. Steele has said that there are portions of the dossier that he considers not entirely reliable. He has said the chances of the veracity of these questionable portions is "50:50". It is compelling that Steele is British and should have no interest here other than truth. There seems to be no question about his abilities. He is highly regarded by the intelligence community as an expert on Russian intelligence.
There is a big difference between proper opposition research (which is based on a candidates public speeches and verified facts -- which plenty exist for Trump) --- and the Steel Dossier (which is a compilation of fabrications and lurid nonsense - where the only correct "fact" is the spelling of Trump's name).
The Republicans funded proper opposition research by Fusion - the Democrats funded the Steele Dossier.
