Quantler?? Free cloud based algo trading

Found it online, this any good? They say it is free

Quantler. com

Compatible with over 250 brokers
Low latency (NY and London) - cloud hosted
C# based, and open source
Tick Data support
Simulate latency, spreads, commissions etc…
Modules marketplace
Compare backtest results (showing how small changes can impact results)

if its free it must be good ........

They also offer a paid version, is that one better?

[EDIT]

Just because something is free, does not make it good by definition, that is why I am asking :s