I have had a look at the index DAX and FTSE which I am usually trading, the spread is 0.90 point, so that is actually ok. I will have a look at the US index when they open in the US. But the platform, I don't know, it will for sure take some time to get used to.
I have found the execution time to be rather slow using the demo account, hard to tell about the slippage. If one always get the price you have clicked on, it doesn't matter that much, if it takes some time for the platform to update the trade.