ERISS: Deluxe is adding a god-mode by adding OP classes, breaking the game, making it boring.
So, if the game is not so complete, we however lose nothing good.
Even if you are okay with the loss of the "OP" characters and items, it also come with a PDF artbook (arguably even less worthwhile), and -- much more importantly -- standalone desktop versions of the first two
Rebuild games (which, with the death of Flash, seem a bit more worthwhile than they might've a few years ago, when they could be played for free on the Web). It would be
very nice to have these available here (and on the Humble Store).
Now, AFAIK, one can still get the Deluxe Edition through the devs' site, delivered through the Humble Widget (and presumably DRM-free); it would, however be nice if they had seen fit to offer the Deluxe version of the game here from the get-go (which -- if the fact that the DRM-free versions available both through Humble Bundle proper and, I presume, GOG are chronically out of date is anything to go by -- is probably not going to happen). Especially since it rarely, if ever, gets discounted on the devs' site.