well, for the price point of Nespresso capsules - you can use third party capsules but at the cost of degraded taste and quality. The nespresso capsules are expensive because the coffee used is specifically selected, roasted, and filled in aluminium sealed capsules whereas most 3rd party capsules use plastic and cheap coffee.
By the way, nespresso provides free home used capsule collection for all those environmentally concerned people.
I still bet, for the price to usability to quality, nespresso is the best. For La Pavoni and similar machines, you need to know to exactly how to pull a good espresso shot, and also how to properly froth the milk at right temperature and texture - aeroccino does it automatically and simply! Moreover, the quality of the foam is amazing compared to the one showed in picture which has huge bubbles and bursted foam - never recommended by a barista!
Enjoy!