What do you like best?
OpenStack is truly opensource project and everyone can use it or change whatever he wants.
For developers it means that you always can know what is under the hood.
For companies it means possibility to try OpenStack or use it without expenses on licenses.
OpenStack has modular architecture that allows you to select a set of services that you need or create and integrate your own service (For example your own billing or integration with services of your company).
OpenStack is fast-paced project that evolve continuously, every new release brings new services and new features.
I like the community behind OpenStack. If you want to be OpenStack contributor, it is really easy.
What do you dislike?
From my point of view OpenStack is not something easy to use.
It doesn't provide smoothly user experience, very often something doesn't work as expected.
I can say that OpenStack is a framework for creation your own cloud, but it is not ready-to-use cloud platform.
A lot of companies like Mirantis, HPE, Red Hat are trying to sell their own "ready-to-use" distributive of OpenStack.
And I feel that it is a really big problem, because big players are trying to create it's own proprietary version of openstack and don't place all changes back to the community.
Big players wants to get a lot of profit from the project with minimum efforts on improving OpenStack.
Just try it and you will see that usability of OpenStack is really bellow any expectations.
Recommendations to others considering the product
It is easy to try. You can try it online. http://trystack.openstack.org/
It has pros and cons, so everyone should decide himself.
What business problems are you solving with the product? What benefits have you realized?
I am an OpenStack developer. I work in Freezer Team - we are doing Backup as a Service product Freezer. Freezer is a part of OpenStack Big Tent (Officially supported projects). We are using Swift (OpenStack Object Storage) for storing backups.
As user of OpenStack, I actively use openstack for testing. OpenStack (as any IaaS) allows me to create VM really fast, without any communication with IT guys, manage my resources. Deploy, install and test my applications.