Well, that was interesting. No feedback at all, so I tried three test sites: posting in the Phandroid "Alpha & Beta Testing" forum, ElusiveStars, and TheBetaFamily.
ElusiveStars gave me five reviews within 24 hours, and cost $20. TheBetaFamily and the Testing forum cost nothing but time, and gave me zero reviews. It's now five days later, and there may be reviews to come in yet. TheBetaFamily review period hasn't finished.
The reviews from ElusiveStars were useful, and (by Western payrates) represented more time than you'd expect for $4 each. According to the SIM info, the reviews were from: USA, Netherlands, India, Croatia, USA.
ElusiveStars advertises $2 per review. I asked for ten, and have so far received five. Even so, I'm happy with the service - I got reviews quickly and cheaply, and the reviewers had clearly given more than a cursory look at the app. One said they'd looked at comparable apps on the app store.