They were worth 30 years of peace. It wasn't a treaty. Everyone knew it was a handshake agreement without consequences for breaking it. It prevented an immediate war in eastern Europe after the fall of the USSR. A war that could have been much worse involving nuclear weapons.
Unfortunately the war came 30 years later.
For something as serious as giving up a nuclear arsenal it’s reasonable to expect to get more than 20 years of peace and for the co-signers to actual fulfil their parts of the agreement, whether legally binding or not.
The end result is that no country will soon trust a Russian non-aggression promise and none will trust an American promise of support.
It is also widely believed to have had a hand in the poisoning of Viktor Yushchenko with dioxin in 2004, in order to give an edge to his pro-Russian opponent, Viktor Yanukovych.
But even if that’s not true there’s ample evidence of overt Russian influence campaigns to support Yanukovych in that election, which was just 10 years after the Budapest Memorandum.