Here are my observations so far. Most of these apply to either DSL or cable modem as they are similar. You can save by dropping a second phone line and any ISP cost. Speed is about 10 times faster. I downloaded 27 MB in less than an hour and pages display almost instantly.
Convenience is amazing.
I leave my e-mail program on constantly and surf instantly. Security is a problem. You must learn to protect yourself from intruders. Being on continuously leaves you more vulnerable. You should install a firewall program.