Belated thanks, folks, for chiming in. A few thoughts...
Roadmaps are important for both driving and software, but for the latter, I still think they're overrated. I prefer to hear and see evidence of broader strategic direction. How much does a vendor really care about a particular offering? Will their delivery model change? Are they keying in on particular verticals? Have they tended to meander in the past?
Google may not issue detailed roadmap guidance, but more important things enterprise customers might want to know about them is how long they are committed to any given offering before they decide to keep it, and whether they will continue a support and implementation model consisting primarily of smaller integrators who have no closer access to Google's systems than you or me. Google's approach works for some customers; not others.