What do you like best?
One of my favorite things about DigiCert is their Certificate Utility. When requesting a new SSL certificate, it can be a real pain to create a CSR and the back and forth to update the request. Digicert provides a standalone tool that handles all this, no need to jump into IIS or whichever web server you are using. It's made it very easy to create requests.
What do you dislike?
The management page isn't laid out very well. It's functional but could stand some usability updates. Using SANs and updating them usually requires contacting support. Their support is usually on top of it though, so it's easy to work around.
Recommendations to others considering the product
Use the Digicert Utility to perform the certificate signing request! It makes it significantly easier.
What business problems are you solving with the product? What benefits have you realized?
Digicert solves our needs for new SSL and code signing certificates. They manage and provide our certificates and renewals in a generally easy to use fashion and get us up and running quickly. Their price is very competitive as well, so it's general met all our certificate needs at a good price.