I think it would be amazing if there was a constitutional amendment forcing all government information to be disclosed within an extremely short period. Someone sues the NYPD, the amendment gets incorporated, bada bing, bada boom, government transparency.
A lot of government information is tied up with individual privacy. For example, Census data isn't released for 70 years, for privacy reasons. I certainly wouldn't want the IRS to release my tax returns, or Medicare to release my medical records.
Of course it's easy to abuse the citizen privacy excuse to hide things that should not be private. But you can't just make everything public without causing significant problems, either.