I stopped with IndieGameStand, most games are rubbish and the ones that are at least decent come to IndieRoyale or HumbleBundle shortly afterwards.
Depends on how you view IGS and what your consumer's habits are...
I personally got fed up with IndieRoyale due to a neverending backlog. Just right now, I could buy 17 games on IR (Debut 20 + Mixer 10) for less than 5€ but I don't care because I didn't even play a third of my past IR purchases. And honestly, I feel just like I would participate to the race to the bottom. Remember the early days of IR when for 5-6€ you got 6 games only? Now, devs get nothing and players just get useless games. I like IGS 4-days deals because as a consumer, you get to really "choose" your discounted game, you have more chance to play it because that game interested you particularly. And from a dev POV, you only get peanuts and if you ever get on steam, those sales cannibalizes a little your launch. Two recent articles from Gamasutra: http://gamasutra.com/blogs/RichardHillWhittall/20141023/228442/Bundles__Approach_with_your_Eyes_Open.php http://gamasutra.com/blogs/RobertFearon/20141027/228628/Bundling_in_2014.php
That reminds me I bought impulsively the recent "mystery" bundle from IR but I haven't yet bothered to open my e-mail with the page/key link in it...
On HB, it's now rare if I buy them too because, I already have the games I was interested in or they don't provide DRM-free versions. And also, the Humble Store sucks big time as a "store" because you can't browse games properly (same could be said about gog btw), your own library is a mess and due to a difference in the contract, games that have an individual widgets aren't necessarly included in the store.
So, while there are some crappy games on IGS (I don't even understand why they allow beta/alpha games), I think it's the best successor of Desura so far as a way to discover unknown games because it gives them visibility and good "store functions" from a user POV.
BTW, Arcen games are currently on sales (up to -85%) but steam-only apparently: https://indiegamestand.com/store/browse.php?tab=on_sale