I don't think this most recent format change is going to increase participation.
I don't want to speak for whole community, but I think that a lot of people disappointed with changes were simply used to the old interface and are not willing to adapt to new one. I've also had some little difficulties with finding myself in it but in the end I find new interface very good. Whole idea of separating lessons from mastering by translations is great - whole process of finishing skill is more diversified and clear in the same time. Providing more information about progress in translating documents and particular sentences is awesome too. Of course some things needs to be improved (I would especially point to selection of sentences for translation according to language level) but I am sure someone is working on it.
There are things I actually like better, the sound seems to work better. The lesson boxes don't bother me at all but not having a couple of translations within the section you are learning doesn't make sense in my mind. Then when I go to the translations section, there's no incentive to even try. Didn't go into this with a closed mind and actually thought it might be better but unfortunately, I'll have to agree with the complaints.
I like the new format! I think it has a nice organization to it - and I like the way the vocabulary is listed in each section. It makes it easier to review the words that aren't as familiar. I would like it if the translations for the words were available with a mouse over the way they are in the main vocabulary section. Edit - I see the translations are available when you access the full vocabulary list for the section.