Looking at the details page, here is a limitation depending on how you handle client accounts, or your own accounts.
What are the Lightsail service limits?
You can currently create up to 20 Lightsail instances, 5 static IPs, and 3 DNS domain zones in a Lightsail account.
But this is pretty cool. Ability to manage traffic before it hits your VPS:
Can I manage firewall settings for my instance?
You can control the data traffic for your instances by using the Lightsail firewall. From the Lightsail console, you can set rules about which ports of your instance are publicly accessible for different types of traffic.