The store is ok but the daily deal has been displaying for me as 'General Error' the past several days - anyone else getting this?

Yes.

Somebody asked about it on their forum but there are currently no replies: https://indiegamestand.com/forum/viewtopic.php?f=19&t=5195

Maybe they don't have a deal to offer for now. Although maybe unrelated or maybe not, but IGS is now dealing with the "Beholder" problem, where a bunch of Steam Keys were given for free almost a month ago, but IGS was also selling that game, and today all those keys (free and sold) were revoked on Steam:

http://steamcommunity.com/app/475550/discussions/0/1843493219426371494/
https://www.steamgifts.com/discussion/1Iv2x/free-beholder-indiegamestand-restocked-atm/search?page=5#k5OztLF

Although, now the developers are delivering new replacement Steam Keys for those with a proof of purchase:

http://steamcommunity.com/games/475550/announcements/detail/704082239832566079