Recently I asked Qwest a simple question -- Must I have a landline in order to have DSL? The answer was "no", and I bet a lot of people are keeping their Qwest phone line because they don't know that. You can save quite a bit of money ($30 per month or so, depending on options) by having Qwest discontinue your home phone service. If you have a cell phone, why not?
Anyone who calls your home phone number after you make this change will get a "disconnected" message instead of a "new number" message, so be prepared for that. I found a way around that problem by "porting" my home phone number to one of the secondary numbers at Golden Real Estate and having it forward from there to my cell phone.
Another consideration for me in not having a landline was my fax machine. As far as I know, you can't fax using a cell phone. The way I got around that is to scan outgoing documents to my laptop, then email them. For incoming faxes, I have an efax number.