Hi H trader & Harry,
Harry - maybe it doesn't help much on your concerns about account protection - but surely interesting to read is the Standard & Poors Rating for Interactive Brokers Group , including it's subsidiary Timber Hill ( used to be the other way around in the past - but times are changing )
You can find it here :
http://www.interactivebrokers.com/download/sp_rating.pdf
Htrader :
yes, I traded on XETRA , but not via IBIS network, as IB is offering it. I think, having access to IBIS is great plus , since this usually the route only the big guys ( banks etc. ) can use in Germany. Look at their bid and ask sizes und you know what I mean.
I have also a german broker-account, because IB offers this MC account only since a few months.
Usually XETRA is very fast and efficient,. because it's a totally computer-driven trading platform - much like an ECN.
And for the top 30 Stocks ( Dax ) there's also enough liquidity. Some of the NEMAX 50 Stocks ( german's mini nasdaq ) are also very liquid.
US stocks on XETRA :
well, this is a special situation, since the so called US Stars is a new segment on XETRA. It is a bit comparable to the Nasdaq Market-Maker system - there are several large US MM's and some german MM's who make the Market for the SP100 and Nasdaq 100 stocks on XETRA. So you'll always get a price , but the spreads are larger than in the US - especially during non-US trading hours.
Liquidity : you'll always get a price. Of course trading US stocks on XETRA makes only sense, if you don't have the time to trade during US market hours or if your account is too small for daytrading directly in the US.
You can daytrade US stocks on XETRA with an account < 25K.
Since IB's MC account is a margin account anyway - you can even trade with 1:2 margin. Something most german brokers won't allow you.
Have yet to find out, whether shorting of US stocks on XETRA is possible.
US Stocks trade in EUR on XETRA, ( and on other german exchanges ) but are, of course, still subject to changes in currency exchange rate USD/EUR.
If you want more info about XETRA, or to see live and for a limited time free of charge, how the US stars are traded on XETRA, follow this link :
http://deutsche-boerse.com/usstars/index_e.htm
Good Luck