Well Microsoft also started giving $120k (first 12 months) in free credit to startups that went through most accelerators, whereas equivalent AWS credit has been exhausted by most of us.
I've heard about this as well - a friend's startup has a vast free infrastructure on Azure using the same program, but I think though you'll be in troubles having to migrate to AWS/GCE when you run out of the free credits and your startup survives one year and migration is the last thing you wanna deal with at that time. :)
Note that for YC, the number is $500k.