The most valuable feature is the very large probe number, over 180, for different technologies, that all comunicate their metrics through one product.
When you are implementing it, I think the most valuable tool is the Infrastructure Manager (a Windows client for probes management and configuration). Of course, there is also a web-based tool, but you cannot do it all from the web interface.
When you are using the product, I think the most valuable feature is UMP, with its dashboards, and alarm view. You can see the alarm state of your system, and pinpoint the most critical elements and metics in dashboards. This allows you to rapidly view and acces the alarm console for that specific element. It is fast and easy to use.
Not for my organization, but for our customers, they managed to monitor their infrastructure in a unified manner, more easily, and at different levels (management, operational etc.).
Although the products is easy to deploy, the implementation effort is still inconsistent. This is because you have a lot of different technologies and vendors.
I started with this product a year ago, and am still working with it.
None, but of course you need basic knowledge about the infrastructure elemets that you want to monitor, and for which ones you want to deploy probes.
CA UIM is a mature and stable product.
I have used and implemented the old product, CA Infrastructure Management, but CA UIM is the new strategic product in this line.
You can try it, or you can try the Snap (CA UIM Snap), unlimited in time, but only for 30 devices and with fewer features, by registering on the vendor site.
If you have a strong IT department, or some special request for monitoring, that is hard to shared with others, you can try to implement it yourself. Otherwise, it is better to have services (from CA or other companies). You just have to remember that it is harder to take on an implementation on the fly and correct what is already done, than have one done from scratch.