I also use O*A*N*D*A for order execution, but I use
MT4 on a
demo account for charting and alerts, as do many others here.
The demo accounts with MT4 expire after 30 days, but its simple enough to sign up again, Strategy Builder has unlimited demo's as long as your actively demo trading with the account.
MT4 is a great charting package, there are however many more custom indicators and advisers available for strategy builder and MT3 and it will probably take a little time for developers to recreate these for version 4.
Version 4 of MT dosnt as yet have backtesting facilities, so you may want to bear that in mind.
Theyre all free and easy to install and use, personally Id install strategy tester for its unlimited demo, backtesting, and good choice of indicators, and possibly MT4 as well. Let me know if you need the URL of websites for download
cheers
mick