Over on the chainsaw forum, to start a thread like this is about the same as starting a "Which is better, hydro-static or gear shift?" thread here.
While many people use straight 30w with no problems, I don't think that there is a chainsaw dealer alive that would tell you to use it. I don't think it's just so they can sell you there brand oil either. I had one guy tell me that he didn't care what brand I used, just use bar & chain oil and NOT motor oil.