DD: Izzet vs Golgari was recently announced and I hope it isn't as crappy as DD: Venser vs Koth.
DD: Venser vs Koth was bad for the following reasons:
1) No Koth art on any of the alternate art cards.
Alternate art Chartooth Cougar, Anger and Plated Geopede is fine and all (not really the first two) but where on earth is Koth?
Feels like they were too distracted having Path to Exile have Plated Geopede in it for them to remember poor Koth.
Preordain had Vensor. That was ok.
The card with alternate art needs to be playable too and not something people wouldn't ever consider for Commander.
2) Crappy decks
I don't see how difficult it is to get a decent deckbuilder to make decks people would enjoy playing. Balancing is one thing that they would actually require a good deckbuilder to do. Have you ever heard about what people feedbacked for DD: Divine vs Demonic or DD: Knights vs Dragons?
The first two DDs were probably the more balanced ones and I'm pretty sure no one grumbled about being on either side.
3) Crappy rares (see Koth's deck)
Some DDs are driven by the cards in them.
As long as people get their value for money from the two decks combined, they wouldn't mind paying. Sometimes, DDs become very good buys like in the case of Elspeth vs Tezzeret. Everyone was happy.
How to do things right:
1) Niv mizzet on Remand. Golgari dude on a playable card like Duress. Do not miss this.
2) Don't make alt art Stinkweed Imp again! New alternate art plz!
3) Don't give us replicas of old precons. Ie don't focus on replicate and dredge.
4) New Niv Mizzet to go with dredge guy.
(full art Niv Mizzet already exists)
5) Balanced decks
Not that I care but it links to the success of the product.
Used to think that Niv Mizzet became a planeswalker because he wasn't around for some time in the story... 2 new planeswalkers would be cool though :)