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:
Nightly Builds!
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.