1) Securing your back-end APIs - If you have a legacy back-end web service that has a basic authentication scheme, you can add some additional security by placing APIM in front, and requiring subscription keys. Leverage your existing firewall to ensure only your APIM instance can communicate with your back-end API, and you've basically added a layer of protection.
2) Lift and shift - there are always going to be clients that don't want to update their clients to use a newer API; in some cases you can make a newer API look like an older one by implementing some complex policies in APIM. You can also do the opposite, making older APIs look new, such as making an XML back-end accept both JSON and XML.
3) Centralizing your APIs - if you've acquired another company and want to make their API set look as if it's a part of the larger whole, APIM is an easy way to provide a consistent front-end interface for developers.
Imperva web application firewall does a great job in giving us control over access to our public web servers. With our regular hosting provider, we couldn't block access based on geography, or really anything. So we had to rely on traditional access controls to protect the data. But with the WAF, we can block countries such as North Korea, or we could stop any SQL Injection attempts, or even do a temporary block of IP in the case of detected brute-forcing.
Alert Aggregation - Correlates different violations into perceived correlated attacks.
Ease of deployment - as one of the only WAFs that allow bridge mode deployment, this can be deployed with without downtime and no Network Architecture modifications. If the need for proxy is required at a later time, Transparent Reverse Proxy can be deployed within seconds and minimal configuration.
Custom Policies - Custom security policies are easy to configure.
Reporting - There are a good amount of pre-configured reports available by default.
Lack of robustness is a bit of an issue. Several other providers offer more options and capabilities, but then, they are lacking in interface ease.
As with anything Azure, pricing is really hard to stay on top of. I always find that you really don’t know what you’re paying for until you get the bill. Having an excellent Azure Administrator can help resolve that.
Integrating with app services outside of Azure can be a challenge, or at least much more challenging than just using Azure App Services.
There are just a couple of points that are hard to find, that probably could be elsewhere. But these are minor; everything else is right where you'd expect it to be.
We haven't needed support from Imperva since implementation. But during that time, their personnel were very quick to respond to questions. Since then, it's been largely doing its thing for us (which is exactly what we'd hoped).
Ultimately, it was the easiest to work with that was still a "known" company (we've been burned too many times by up-and-comers). We needed something that gave us a lot of control but then didn't need its handheld on a daily basis. Imperva gives us a lot of that and we are still able to navigate it with ease.
Better Insight into web application - Absolutely great, checks all the traffic against RFC standards and will alert on common development mistakes that duplicate application traffic or provide attack vectors for potential attackers.
Have had several issues blocking a customer without producing alerts, while it happened only one week out of 2 years of working with the devices, it did produce a lot of headaches.