The turning point for me was when we discovered that it would replace the need for the second phone line. They do not interfere with each other in any way. When your system is powered up and properly configured, it is hooked up. Depending on your ISP, multiple systems can be surfing simultaneously through an Ethernet network. If you have more than one system you will need a hub.
Performance is impressive.
This goes for surfing as well as downloads. Downside DSL is not available to everyone. Your line must qualify. Many lines in Tucson do not. US West has begun some programs to improve that situation but it may be a long time before everyone can get it.