I'm a trader and writing this from a Mac with windows 7 on it & I've been a Mac user for the last 10 years. What I mean is that you'd require Windows to run most of the TechAnalysis software out there, so a virtual machine to run windows or a dual boot windows installation on your Mac might be the option. Other than that you can also go for a PC (I did that to have a stable trading system).
Coming to TA software. The best one's I've heard are TradeStation, eSignal, NinjaTrader, SierraCharts, Amibroker & Metastock. Tradestation, eSignal, NinjaTrader & SierraCharts are subscription based some of them are free to try and free to use offline but not to trade live (best out of them I'd say are TradeStation and NinjaTrader).
But if you require a TA software with powerful tools that is not linked to a broker then Amibroker and Metastock are great to work with. Metastock has it's limitations after a point in that you cannot make use of loops and multiple-time-frame analysis. Amibroker however is the best that I've come across. It supports multiple time frame analysis by default and also has looping and pretty much everything that a TA software should have under the sun. It also integrates with most brokers to send and receive data and orders. It is also upgraded very regularly and comes very cheap, and is also light on your computers resources.
I was a Metastock user before I switched to Amibroker permanently. It's the best software out there.
(That should be enough info, hope that helps).
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