I've now tried Spotify, Tidal, and Deezer. Tidal wasn't enough to pull me away from Spotify. The first week or two of Deezer wasn't either...Honestly it was the available music on Spotify that kept me (and marketing and customer loyalty, I've used Spotify for years). The quality on Tidal and Deezer is hands down better than Spotify on average. You will notice an improvement and, to be frank, I don't think that has to do with lossless/hi-fi. I think it's the source quality.
After more time with Deezer I realize its catalogue is actually larger than Spotify's and the quality is better. Lossless is awesome too. So unfortunately, I'll likely be ending my Spotify subscription. I'll check back if they add lossless, but many people have been asking for it for a long while. I think Spotify had every chance here, but just didn't deliver. I really don't think Spotify cares about lossless because I think it only serves a very small subsegment of users.
If you want lossless, I would suggest Deezer. I do wish it was like $5/mo cheaper. I think if Spotify came in with a more aggressively price lossless option, it would really spell trouble for Tidal and Deezer. Though again, I also don't think Spotify is ever really going to invest much into the audio quality department. I bet 95%+ of their users are using cheap earbuds. All lossless would stand to do is run them a higher bill. I absolutely can't fault them for that business decision and I absolutely had a lovely time with Spotify over the years.
I'm in the same boat. Started a long time ago with Google's Play Music, then switched to Spotify, but the sound quality occasionally was plan and simply horrible. It wasn't just the streaming, if the source is fine, 320 is not bad, but not good either. I am a sound engineer, so lossy music on studio equipment sounds horrible no matter the source. And it's all i have, studio equipment. So i ditched Spotify, turned to Tidal. At first, it was ok, but i noticed the same thing on their lossless stream, occasionally the sound quality was subpar. So they too have "source quality" issues. But the UI was horrible. And it's heavily rap & rnb oriented, too much for my tastes. And so i ditched Tidal as well and turned to Deezer. So far, i have the best experience with them. Nothing is "the best" with them, but everything works good enough. Sound quality very good, sources are good, UI acceptable, "flow" works good, track suggestions work fine.. Spotify excels at suggestions and user experience, but lacks sound quality. So, concluding, Deezer is my choice until Spotify starts streaming lossless and verifies sources.
I am 100%in the same boat as Steve83 above. I also pay for both Spotify family and recently gave Tidal a try. I kept hearing how bad the interface was, but I actually really like it. I'm impressed by the SQ of their FLAC based media and really enjoy the MQA content as well. The tidal interface gives a ton of info about the recordings as well as a great mechanism for RIYL. I don't want to give up on Spotify because I've been a subscriber for 6 years. But, if the status quo in terms of the sound quality is the best there is I'm going to make the jump completely.