They're as reliable as GE, Snecma, and P&W. Anybody can have an uncontained failure at any time. It was a GE CF-6 that lost the fan in the #2 engine on the UAL flight at Sioux City. American had a P&W JT8 fall off a B727 over the desert Southwest, Piedmont had a P&W JT8 fall off a B737 at ORD, USAir had P&W JT8 fall off a B737 at PHL. The Rolls RB211 is prone to engine annulus fillers (fan blade spacer) leaving the hub (contained failures). USAirways had an uncontained turbine failure of a GE CF6 at PHL during a maintenance run. AA had an uncontained turbine failure of a GE CF6 at LAX. The list goes on ad nauseum.
Any engine can fail at any time. A lot of the reliability is dependant upon the care the engine receives while in service, in addition to the manufacturing process and the overhaul processes.
I personally, am comfortable with anything P&W, GE, Snecma, or Rolls powered.
We need to give the investigation a chance to see what caused the uncontained failure in the A380 and not jump to premature conclusions. It could be due to a one time event, or it may be the harbinger of a trend that is just manifesting itself. I'm sure due investigative diligence will occur and the culprit will be identified.
I thought Qantas took exceptional steps when they grounded the fleet due to the unknowns to this point, and definitely have passenger safety in mind.
Airline A&P for 27 years and counting.