You might lose the Yoda revelation... but it is such a short period of time in which it takes place (from meeting Yoda to learning who he really is) that it's not as big of a loss. It's hard to remember some of the "surprises of the OT"... I'd completely forgotten that first time seeing it where you think he's some random alien there to get on Luke's nerves.

However, I will say that the PT changed it to a different revelation... the revelation that to a certain degree, Yoda did go a bit nuts on Dagobah. I think for a first time viewer watching films 1-6, they might seriously be in shock "Oh my god - That's Yoda now.Wtf happened to him??!!"