I posted an overview on TradeStations software and brokerage platform under the "Brokers" subsection bc I figured for most day traders paying for trading s/w and possibly data feeds without being able to directly trade from the platform makes no sense. Most traders therefore will have to make a decision about signing up for both the use of the software platform as well as their brokerage services.
There's also been a few threads from others so search the site for those links to read up more about TS too.