Bada is interesting in terms it is doing just the reverse MeeGo is doing, while MeeGo is trying to make a unified base that can be fitted with a Qt API (which is in turn universal across other OSes), Samsung is fitting OS-es (or, rather, kernels) INTO their API. Due to this, Nokia's approach has a bit more resource overhead, but on the other hand is easier to maintain and is more universal - as it can easily spread to new OSes (we already have - even if unofficial - Qt for webOS and Android, and a sterling but doomed iOS effort). Plus, as a bonus, it can be retrofitted with very little effort to tens, in not hundreds of millions of existing handsets. As for Bada, the 'low-end' part of the platform has not been released yet, so I can't comment just how well their unified approach works (contrary to Nokia, who have demonstrated Qt working nicely on midrange hardware of 2008).

EDIT: When I say 'not released yet' I mean the new range of low-end spectrum, not the existing, pre-Bada-is-now-cool phones. Also note that Bada is not really aiming for top-tier - the Galaxy stuff is Android, and even on the Bada pages, Bada is positioned more like the OS Samsung wants featurephone users to migrate to - very much the position of Symbian in the Nokia ecosystem. The problem with this is that I don't see the bridge between Android and Bada (the role of Qt in Symbian-MeeGo), and the popularity of Android makes it difficult for Sammy to push Bada into that segment without hurting itself at least on the short term.