I haven’t heard anything about Apple suppplying a way to turn off or modify the transparency of the Leopard menubar. There have been mentions of third-party hacks to do this.
I am thinking it might be one of those things that bothers you from a screenshot, but when actually using it, the feature might please.
I think the “leaning tower of Pisa” effect in the Stacks feature looks terrible. Have to wait an use it before making a decision though.