What does the software or service do well? Dreamhost is particularly notable for providing excellent technical support. I've been using them for all of my web hosting for over 10 years now and never felt the need to switch to anybody else. Their hosting service is reliable and I'm generally happy with service and site speed.
What does the software or service not do well? I do sometimes have issues with my email autoresponders, which always requires help from support. They resolve it every time but it still happens frequently.
What do you wish you had known about the software or service before using? As with most hosting firms, there's a wide range of different subscription options, so choosing the best thing can be a bit of a challenge, as can making sure you're getting the best possible price.
Have you used a competitor to the software or service? If so, how does it compare? I've used many different web hosting firms, both good and bad. Dreamhost strikes a good balance between price and performance.