You're right Gizmo, there is a large discussion about Skies vs. Fires going on right now ( esp. on Mindripper). And it mostly favours Fires especially after Chicago and Planeshift, with the inclusion of Flametounge and Simoon in most Fires decks.
The problem for Skies in the matchup as I see it, is that it can never permanentely remove the threats that Fires cast against it, except with the help of counters, of which it has about 8 of. The Washouts and Withdraws just stops the Fires for a while, and the Skies very seldom has the amount of creatures to be able to put pressure on Fires.
Since there is no need for Fires to get defensive the Washouts just stops it for 1 or 2 turns without really damaging it.
The reason why I wanted to include black in the Skies, even if I am sceptical to it, is that it allows Skies to clear the board permanentely (with the help of Perish/Decree)of Fire's threats, instead of just buying a turn or two, which really don't make any difference. Without any permanent removal I hardly can see how Skies will have an sort of favourable matchup against post-Chicago Fires.