[Boromir88]

Originally Posted by Legolas

He spent time out east where Sauron and Morgoth had influence dating back to the First Age. There's nothing contradictory about suggesting he could've picked up certain arts - even specifically some of Sauron's arts, as you say - or just mentally came closer to succumbing to his own desire of power.

I agree. Saruman is perhaps my favorite villain created in literature, such a fascinating lad.

Anyway, his personality is someone who loves to study things and absorb knowledge. Even if he wasn't evil at the time he went East, his personality (like Boromir's) had little defects that if unchecked would definitely lead down a path to evil. He was proud (led to lusting for power to the point that he was blinded by it and I would say even paranoid about losing his authority) and jealous of Gandalf, even back in Valinor, but especially after figuring out Gandalf had been given one of the elven rings:

And the Grey Messenger took the the Ring, and kept it ever secret; yet the White Messenger (who was skilled to uncover all secrets) after a time became aware of this gift, and begrudged it, and it was the beginning of the hidden ill-will that he bore to the Grey, which afterwards became manifest~Unfinished Tales; The Istari

And taking into account what Treebeard knows of Saruman:

"...he has a mind of metal and wheels; and he does not care for growing things, except as far as they serve him for the moment."~Treebeard

"I used to talk to him. There was a time when he was always walking about my woods. He was polite in those days, alway asking my leave (at least when he met me); and always eager to listen. I told him many things that he would never have found out himself; but he never repaid me in like kind."~ibid

The sentenced I bolded reveals a lot about Saruman (even in days when he was polite and "gave no trouble to his neighbours" - as Treebeard put it). He was a leech, a leech for knowledge but never "repaying" what he had learned. If it was of interest, and useful to Saruman he would take it, but he was not the giving type.

So, travelling East with the Blue Wizards I would say that yes, Saruman would have absorbed whatever knowledge he had a mind to take. We know that it was his devices which ultimate drove Sauron out of Dol Guldur too. This thirst for taking knowledge, yet not sharing any, probably contributed to his treachery. So, I think his knowledge of Sauron's mind and schemes (not to mention the study of Ring-lore) was unrivalled, even by Gandalf. At least until the time when Saruman falls to his lust for power, he becomes blind to the fact he has become a generic brand of Sauron.