I have been using Cornertrader for stock investments because they do not charge custodial fees for stocks. On the whole I have been satisfied with their service. Representatives are quick to respond to emails and phone calls.
The platform itself is more limited than Swissquote and Saxo Bank (I've tried the demo versions of those) for frequent trading (i.e. CFD and forex) due to the absence of trailing stops and other more advance features. You also don't get a huge reach as far as alternative investments (i.e. shares listed on smaller stock exchanges), but that isn't unusual for online trading platforms.
Brokerage fees are not as low as those offered by some international brokers, so you will definitely want to save and buy larger amounts of shares per stock purchase so the brokerage fees don't nullify your chances of making a profit. But because I earn my income in CHF, I lose some money on the exchange when transferring to my foreign broker, and I prefer that my shares are sitting here in Switzerland where I know the legal system. Because I buy shares to hold them for dividends and long-term capital gains, the absence of custodial fees is more important to me than low brokerage fees. I use a different CFD trading platform for CFD trading.
I would recommend Cornertrader to buy and hold stock investors in Switzerland who invest in Swiss and mainstream international stocks.