How is it with the timing. Is it the right time to do what you want to do?
Be honest with yourself. Is this a right time to launch this product? Often times the timing is actually more important than the product itself.
Case Study: Before Skype came, there was Dialpad. Dialpad was popular but because there was an issue of bandwidth problem, it slowly died down due to the bad quality of conversations.
Zynga wouldn't have been possible without the rise of Facebook as well.
Introspect carefully and see if there are any timing advantages now that makes sense for your startup. This is not crucial, but has been a key factor for the failure or success of many startups.