Agree, wholeheartedly.
I've pined for the past couple years to apply functional programming to all my application domains. A recent realization is functional programming simply just doesn't map to many problem domains. Key business logic such as actuation and user interaction often blows referential transparency (i'm finding that pure functions are better applicable in purely computational domains; personally, I just don't spend much time here).
That said, the quest to eliminate mutable state in hopes of achieving pure functions has, at worst, led to more maintainable code. (Simply -- striving to minimize crossing code boundaries with data, and especially references to data or objects, for all levels of procedural abstractions, down to structures)
I've found functional programming and object-oriented programming (see also "pants-oriented clothing") are just two roughly-orthogonal components to the bigger picture -- service- and actor-oriented programming.
OMG, AQ, Scala; you're right. All this shit does converge to something useful.
(A CLA Summit that focuses on practical LabVIEW implementations of programming paradigms; that's a CLA Summit I'd go to.)