1. Democrats should no longer assume they have a better ground game and Republicans rely on voter suppression. Walker and the Wisconsin GOP got their people to the polls in very impressive numbers.
2. As someone who supported the effort to trigger a recall and supported the recall, it is surprising to me how many people voted for Walker on the theory that recall was inappropriate. It is not clear to me, given the very few data points available, whether this is a widely held view (California ten years ago being the one counter-example I can think of). It certainly provides a cautionary lesson with regard to the use of any extraordinary process. The difficulty is that the triggering event occurs well before the recall.
3. Republican tactics were effective in drawing out the process and in the overwhelming use of advertising. Certainly the message that a recall was inappropriate coupled with voter fatigue on the recall appears to have had impact.
I shall note in passing that the analysis of such tactics, and their success, does not invalidate the result. Unless Democrats can find a way to neutralize the significant money advantage Republicans are likely to continue to enjoy, they will continue to lose.