Are there alternatives to a traditional dimmer switch?
As far as I know humming is produced mainly in the core of inductions (coils, transformers) built into dimmers and voltage converters.

Unfortunately all of these 230V LEDs have their own voltage converters, with dimmeable LED's usually sensing the phase cut angle and adjusting the LED chip current accordingly. So you probably may not overcome the humming inside the LED itself. Maybe the only way to have humming free LED light is to use LED bulbs without any current shaping electronics (e.g. 350 or 700mA LEDs) and matching PWM dimmers.

As far as the dimmer is concerned, there are products from Osram, Tridonic and others that are fully solid state electronics, well encapsulated and shouldn't produce humm by themselves. They work on bus systems (DALI, 10V, KNX/EIB) as well as on tap switches.

Regarding off/lo/high ... Ledon produces a LED bulb with "double click" feature, where you use an ordinary on/off switch to switch between off, 30% and 100% ... I saw it in operation recently - very sexy ... other manufacturers are following - search the net for "double click light"