What do you like best?
Renting out their retail platforms' idle capacity, Amazon started a really good thing. Thanks to their initiative, we can now have as many computers as we want, without the overhead or frustration of purchasing, maintaining or troubleshooting them!
Quite fast to start-up and shut-down
Now offers per-second billing!
Blazingly fast in-VM internet connectivity
Close integration with other AWS services - sometimes with free/reduced transfer costs
Ability to snapshot, image and relaunch, reproducing the exact past state of a machine
Tight security, auditing and thorough monitoring
Free tier allows you to run one EC2 instance for a complete year (no downtime)!
What do you dislike?
Having to update the security rules every time your public IP changes, in order to maintain continued access - avoidable by relaxing security group rules, assuming your SSH keys are securely maintained
Missing some very basic yet vital monitoring features - e.g. there is no built-in way to receive a simple alert when your disk is full!
Lack of useful base images below 4GB in size, which means hindering the efficient usage of the free storage (EBS) tier
Recommendations to others considering the product
Carefully consider the instance type you are going to deploy (hourly rate, network/disk performance, memory capacity etc). Overprovisioning and underprovisioning are both equally bad during the long run.
Try to utilize cheaper alternatives to On-Demand instances, such as bidding-based Spot Instances, for significant cost reductions
Upfront payment for Reserved Instances can yield significant cost savings (up to 75%!) for long-term usage. Check out https://aws.amazon.com/ec2/pricing/
What business problems are you solving with the product? What benefits have you realized?
Hosting internal-use services that cannot be provisioned via serverless and other types of deployments
Performance testing (http://esbperformance.org/) of our product stacks, under exact reproducible conditions
Hosting product demonstrations for prospective clients
EC2's low cost, high performance and excellent SLA has boosted our productivity and saved us much of the maintenance hassle over the past several years.