Older Volvo Turbos seem to have a good reputation. I don't know about the newer ones. A turbo uses the rapidly expanding hot exhaust gas to spin a vane as the exhaust exits the manifold. That vane is one one end of a rod, the other end has another vane that is in the Intake air pathway. Spin the unit faster by having more exhaust pass by, and the intake air pathway becomes more pressurized by the spinning intake vane. When your intake Valve opens...more air is forced into the cylinder, so, more fuel can be sprayed in there by the fuel injector, the result is a higher compression ratio and more power.
It's a simple concept. The devil is in the details, such as all the electronic feedback mechanisms that must work in harmony to achieve the highest efficiency, as well as prevent "over-doing-the-boost-pressure". And, it tends to be a hot-natured thing, requiring more attention to oil cooling as well as water-cooling the turbo jacket.
What I'm trying to say is: the mechanics of it are simple, and reliable as long as they are cared for as specified in the manual. The glitches happen when the care is sub-par, OR, when one (or more) of the sometimes fickle electronic sensors fail.
If you don't work on cars, it's not a big deal...you just take it in when it acts up. If you like to work on cars, the electronics can be a nightmare, unless you REALLY like to work on cars and have all the diagnostic tools available.