Primary drawback is they don't take bitcoin.
On Indiegogo you can set up "Flexible funding" where you're given the money even if your goal is not reached (Indiegogo takes 9% fee vs 4% when goal is reached), and you can let people know in the campaign's text that they can contribute with bitcoin as well. It's not against the rules, I know from personal experience. Not sure about Kickstarter, they might be more strict with this.
Indiegogo is what we'd use if we did crowdfunding.
We are looking to go the same route that
https://onlycoin.com which is accepting pre-orders once everything is established and we have perfected the prototype and release videos and pictures.
That way we could accept both Debit/Credit and Bitcoin for pre-orders, and use the funds from pre-orders to buy materials.