Had my 818 for just over a year now. It's performed flawlessly in that time and it's in use pretty much when I'm at home. It's used in a 2.0 configuration, no interest in multichannel movies or music, and in any case, my home arrangement doesn't allow for that. I bought the 818 because I wanted an amplifier that would give me all of the formats I needed an amp to cater for, but without sacrificing the sound quality I'd get from a good quality stereo amp. In any case, I'd felt for some time that traditional integrateds were falling short in their capabilities for 21st century audio needs.
With the breadth of sources available, the amount of formats going and an increasing dissatisfaction in the logic employed within the "traditional" audiophile circles in the printed media and on hifi fora, I had bought Onkyo's TX-8050 networked stereo receiver back in 2011 and had been blown away by how good that sub-£500 receiver acquitted itself. Handling FLAC as it did, this was a revelation in one fell swoop. With the option on the 818 for additional formats, the means to handle DSD natively and giving me ample power to two channels as I'd ever need, with good damping factor (as good as Sansui's AU-717 which I'd also had some time ago) I didn't think Onkyo were doing a whole lot wrong.
In truth, I'm delighted by not just the functionality on offer, but the sound quality which is excellent. It excels with music, movies and whatever else I throw at it (internet radio, PS3 games, streaming, etc...). For the money I paid, it was a steal. One of the best amps I've owned and I've been through a few and auditioned plenty more. The only thing I'd change it for would most likely be another Onkyo AV amp or a hobbyist whim for an AVI Lab Series amp or an Onkyo A933. Job, as it were, done.