To clear up a potential misconception, the availability characteristics of the new dev plan will probably be about the same as before. It is just that historically Heroku has had a hair-trigger about reporting any shared database being offline, a practice that continues now.
Besides considerably better production/dev parity in the higher-level paid plans versus the aging shared Postgres 8.3, the biggest feature I'm excited about is being able to connect directly to the shared database such as via "psql". One can also run pg_dump/pg_restore directly to their local environment, which for development purposes with small amounts of data can result in drastically faster backup/restore cycles between one's computer and Heroku than what PGBackups can provide.
Besides considerably better production/dev parity in the higher-level paid plans versus the aging shared Postgres 8.3, the biggest feature I'm excited about is being able to connect directly to the shared database such as via "psql". One can also run pg_dump/pg_restore directly to their local environment, which for development purposes with small amounts of data can result in drastically faster backup/restore cycles between one's computer and Heroku than what PGBackups can provide.
Disclaimer: I work for Heroku, on data stuff.