We're a pretty popular service, our users are currently sending 100000+ SMS messages (projected 180k this month, and continuing to grow) per month. We're currently using a primary domestic provider that doesn't provide bulk rates and doesn't provide short code access. We're using a few backup providers as well for max redundancy, but aren't thrilled by 'em.
We're ideally looking for a service that provides good bulk rates/incentives, good uptime/redundancy/reputation, easy API-integration (including respectable error codes!) ;). Right now, we're looking primarily for a domestic US SMS solution, but aren't averse to using the same provider for both International & US.
For those of you using bulk SMS right now - what are your recommendations, experiences, etc. in the bulk SMS domain? It sounds like I'm looking for a golden unicorn here, I know, but any data/recommendations/warnings you've got are helpful!