Disclosure: I am associated with quantindia.in
I've been doing algo trading for the past 5+ years. Have tried many things - excel-based trading, own .NET desktop app, Zerodha NEST, Zerodah Pi, ... I believe algo trading is a great way to trade and it should be fully automated - no manual intervention whatsoever.
Have even coded s/w to extract real time data from broker terminals.
Most of the commercial platforms such as amibroker, metastock, Omnesys NEST, etc. provide proprietary scripting languages. I learnt the hard way that if you try doing something different from "standard indicators", you will have to do lot of work to get it working. For example, mixing of candle sizes, trading same algo on different segments, creating your own indicators, money management, what-if analysis, etc.
Suppose you simply want to implement a custom-made trend following strategy without any standard indicator. This may (surprisingly) be nearly impossible to do to your full satisfaction in many tools. Sometimes, just creating an Options trading symbol string may prove very difficult!
I call it the "algo-on-rails" problem - tools work great as long as you code within their way of scripting. Anything outside, you can get really stuck.
Suppose you get it working well and you want to invite your friends/traders to use it. Then everyone has to have their own separate installation & you will have to share your code. IP is gone. You don't even know how much they are actually making (or losing) to pay your profit sharing.
These are some of the reasons why quantindia.in was born - limit-free, fully automated, subscription-based algo trading, coded in perl/python scripts with complete online tracking.
Will share more as time permits.
Happy trading!