Ref Rex - they are good operator but I will attribute their success to Kim Hai leadership and his team rather than any particular aircraft type. Those guys will make it work using any equipment, no doubt.
It is true that there is no direct replacement for SF340 on the market, other two - EMB120 and Do328 are even worse to operate, however as I said there been a number of operator switching to 50 seaters. ATR42 will burn marginally more fuel but it is considerably less expensive to maintain. To quantify fuel, 10% fuel burn penalty is 50 dollars per hour while maintenance gap is measured in hundreds. CT7 overhaul price has skyrocketed over last few years, it grew 50% on my eyes over just a relatively short period of time.
Saab Aerotech is quite good in supporting operators, no complains on this front, but the costs are way too high.