First of all we don’t plan to support Firefox 4 in the DownThemAll! 1.1 release series.
But DownThemAll! 2.0 will be Firefox 4 compatible!
The 2.0 Beta releases we did so far already declared support for some older Firefox betas. We won’t however release a new beta version with every Firefox beta. Furthermore the DownThemAll! 2.0 Betas won’t be upgraded to newer Betas (you have to manually install a new beta, or wait for the official 2.0 release).
If you’d like to use DownThemAll! with current Firefox 4 Betas, then please install our:
Those have the advantage that they are updated once every night, so you’ll always get the most recent stuff with automatic updates. This can, on the other hand, be a downside as well, as those builds can contain more bugs, however they were pretty stable recently. 😉 Of course, Firefox 3.6 users are welcomed to try the Nightly Builds as well.
For a list of changes between DownThemAll! 1.1 and 2.0-dev see e.g. the dTa 2.0b3 changelog.