What do you like best?
Yosemite runs faster on my older machines than any of my previous OS Xs, and it has added some features that help me from having to step away from my computer like being able to make and receive phone calls straight from my computer. Safari is faster and cleaner looking in Yosemite than it was in Mavericks, and it is a nice addition to my browser options alongside Google Chrome and Mozilla Firefox.
What do you dislike?
Many of my work applications took some time to be compatible with OS X Yosemite, so I could not upgrade immediately and had to work to get some of my applications to function normally. Yosemite is old enough now, however, that this should not be a problem for people looking to upgrade.
Recommendations to others considering the product
Absolutely upgrade to Yosemite if you are running an older OS. It will make a difference performance wise on your Mac, and it is incredibly easy to use if you are familiar with any previous OS X.
What business problems are you solving with the product? What benefits have you realized?
Notification center, making and receiving phone calls, and other simple iOS elements built into my desktop keep me focused on my computer and away from my phone while I am at work. Spotlight seems to run faster for me than it did on Mavericks, so finding old documents and quickly accessing programs not on my dock speeds up my workflow.