I was once a Verizon/GTE dsl customer and I have recently contacted them to restart my service now that I have moved into my new house, anyway UPload speeds are always slow no matter what they quote you due to the bandwidth they allocate for uploads, Most times when I had issues with the speed of downloads such as you mention are the result of the site you are trying to download from. It doesnt matter if you have a T3 line piped right into the back of your computer if the site you are hitting is getting 50,000 requests and there server is an old p5233.
My advice is stick with it, Modems blow and you would hate how much slower it would be without your dsl
Also if your ISP is also Verizon that may be part of the issue because I was reading that they are at almost full capacity for what they can handle, so maybe switch ISP’s
I work for Verizon (in Data Services, where I sometimes take the DS3s out of service just for funzies) and I don’t have VZ DSL, even at the employee price. Make of it what you will.