EnterpriseDB claims it is scalable and Oracle compatible (quote: "most applications written for Oracle will run without modification). It is based on Postgres so, I am really confused if "scalability" should be understood as "fast enough". Postgres and "speed" has been antipodes for so long :)

OK, having poured some sarcasm, it looks interesting :) It would be great if it can really do the job, becase - I do not like Oracle :)