What do you like best?
If your work requires you to work with xml, this suite of tools is mandatory for you. Define, modify, analyse xsd and xml in xmlspy. If you need to do data transformation via xslt or other, mapforce is what you need. Its drag and drop interface makes it easy.
What do you dislike?
I've been usin these tools for over 8 years, with at least one new version a year. Don't see much in terms of changes accross the versions
What business problems are you solving with the product? What benefits have you realized?
I use this mostly for system integration purposes, data transformation between systems. Data exchae between Sap ECC and other platforms, including Siebel and web ordering platform.