Very good indeed. If you are Assad..
These ISIS lunatics need to be stopped, and if the Russians have at it, that's all well and good.
Had the US-led initiative quickly disposed of ISIS, then perhaps Assad could then be brought into line or disposed of, without the ISIS question muddying the waters. Sorting out Assad becomes immeasurably more difficult with Russian forces stationed on his soil.
Vlad will be able to get whatever he wants from Assad once ISIS is no more.
"OK Bashir, we're outta here, job done".
"No, no, please stay. The Americans will kill me".
"Well that comes at a price. I want, X, Y and Z".
"No, it's too expensive"
"Ok, seeya"
"Oh alright then".