I've just been accepted on AWS Activate and am really pleased about it!
It's not just the financial value, although this is great: $5000 in AWS credits and $1500 in AWS support plan credits will basically cover all the hosting costs of my startups over the next two years.
I'm choosing to see it as a vote of confidence in my startups and that's a great motivator. Also, since I'm not counting the pennies regarding hosting I'm able to build things faster.
For example, I'm building twitMate at the minute and have just set up a LAMP instance on AWS Lightsail. Without AWS Activate I'd have spent a few days setting up the built-in database that comes with the instance (configuring backups etc) and saved £15 or £30 a month. Instead I just added a managed database where all this ready.
I've yet to use support but I can see this being really useful in future when things scale (hopefully!). It could save a lot of time digging through AWS docs and reading posts on Server Fault and Stack Overflow. I'm a solo founder so I don't have colleagues to go to for help when difficult problems arise.
If you're building startups I'd recommend checking out AWS Activate and applying - it could be worth the effort.