I've not read the whole thread, but in response to OP's original question....
I traded with IG for a good few years but have had some issues with them over the last 6 Months or so and their recent change to their own (crap) basic charting package was the final straw. I tried working with their development team to get the charts fixed but gave up in the end and closed one of my accounts in protest. (I still trade another small account with them because they are generally the best for execution during extreme market volatility).
So, shopping around I tried some new providers. Hated FXCM, had some issues with City Index and eventually settled with Capital Spreads back in August 2011.
There were some fairly serious issues with Caps in the first Month or 2 and they were not resolved satisfactorily (well, not in my favour anyway), and you can read about these on the Capital Spreads thread. But still, I've continued using them mainly for swing trades but also for some day trading. I don't use their charts though - I use City Index basic charts for a quick intraday look and pro realtime charts for detailed analysis (same as IG's advanced charts).
Don't know why, but my day trading percentage wins has been consistently higher using Capital Spreads. Could be coincidence, could be the clean look of the platform or the layout of the platform, or could be the simple format in which you can track your trading history, whatever it is, my (day trading) profits have increased.
There are occasional issues with the Caps platform, occasional issues with spikes on minor FX charts, none of which have reached my stop loss or limit orders so don't know how they would manage this if I lost through it. I did receive an email notification saying a trade had been stopped out at my stop level and I knew the price hadn't been to that level, but when I logged in the trade was still there so I'm guessing they automatically re-instated it.
There are rare times when the Caps platform gives delayed quotes, or even when the price of an index freezes completely. Had an example of this recently when I entered a day trade and the price was going in my favour but the ticket was frozen and showing me as being in a small loss. About 5-10 mins later the price reversed and went miles against me, but the ticket was still showing the small loss - so I took the loss and reversed the trade with a larger stake. The ticket stayed frozen for another 5 - 10 mins (still showing my entry level), whilst price continued significantly in my favour. Suddenly, the ticket unfroze and I banked a very nice profit. Pretty much a once in a life time event but it felt great and I felt like I'd recovered what they owed me from the original issues I'd experienced shortly after opening the account.
Caps do have more slippage than IG but I've found that the slippage is equally in your favour as it is against you, unlike with IG where it has only ever happened against me.
I've come across issues with IG skewing spreads and this has cost me in the past, but not had the same issues with Caps.
Overall when considering all of the options, and even comparing the costs of trading with a direct broker, I'm happy to trade with an SB firm and I'm generally happy using Capital Spreads platform.
