I saw the last Gadget show when an audio expert and a musician plus a large'ish audience where asked to differentiate between MP3 and lossless. First it was through Headphones then via a high end system.
I can't remember the exact outcome but it was far from clear cut with probably as many guessing wrong as correct.
I've just compared Brubeck's 'Take Five' on Spotify Premium/OggVorbis with my Flac stored version through Headphones. I am pretty sure I can hear the differences, both in Bass and treble. The Flac version sounds very marginally cleaner and better defined with firmer bass and better extended/less brittle highs. However, the differences are minute and I am not sure I could unfailingly point out the differences through my system in a blind test. - I can also understand why some may find one prefereable to the other. The Flac version, whilst more detailed and 'hifi', has somewhat less drive or energy whilst the OggV one seems to have more drive and subjectively a slightly more organic sound (Volume equalization switched off).
To be honest, I could happily just live with the lossy versions but appreciate that to wring out that last tiny amount of information/detail, lossless is still ahead and brings some benefits. The higher resolution your system is capable of, the more this applies probably.