I have tested 57.6 vs. DSL connection at my work using two computers side-by-side. When I only track the ES, there is no difference. When I add 100 stocks to the datafeed, the 57.6 modem can start choking.
Also, in my opinion, the problem with dial-up is more dropped connections while trading. Sometimes you can manage to stay online for days but sometimes it just drops the connection.
It generally takes me around 2 minutes to get back in operation after a dropped connection at my house, but then you're missing tick data and have to screw around with reloading tick data over a 57.6.
If you were trading futures and your connection went down in the morning, 2 minutes could seem like an eternity.
I am very upset because my phone company says we are 1,000 feet or so too far from the switching office. I don't understand it, but if the DSL signals can travel 15,000 feet, what's up with the extra 1,000??