After some procrastination I got around to trying Tidal yesterday. I had been relying heavily on Spotify for the last year or so for digital, when I'm too lazy to spin my vinly. Well, I'm now quite sold on the Tidal $20 a month offering and have made the switch. A few main points:
1) The sound quality difference is clear, particularly clear on some tracks which I'm intimately familiar with. I now think I've been silly to play with an uncompressed solution up until now. It's really quite a breakthrough to get uncompressed streaming - a bit of a revelation really.
2) I actually prefer Tidal's interface to Spotify. It's cleaner, less busy, less 'c$%p" everywhere. I just hope Tidal doesn't try to copy every Spotify feature. The interface and feature set is perfectly fine as-is.
3) Catalog feels like it may be less than Spotify's, but to Cerrot's point above, it's surely getting better, so that should fix itself over time.
4) There seems to be some stability issues with Tidal, but I've had plenty of crazy stability issues with Spotify's client too. If anything I expect to be happier in this respect with Tidal as it has fewer 'stuff' going on (For example, Spotify keeps suggesting to me what my FB friends are listening to. I actually don't give a what some random friend is listening to). If anything Tidal feels a bit more stable through Chrome vs. using a standalone client - it's possibly consuming a lot less computer resources and it really feels, looks and works quite fluidly.
5) As 2bgeorge noted above, the key downside I'm experiencing is that I was using Spotify's iPad app as a remote for my desktop (source). Strangely it took Spotify eons to actually launch that feature, but it is great (It has some stability issues too, but generally works ok). I began to leave feedback to Tidal about this on their Help site and there was a recent/related response from them noting that they are working hard and fast on this feature, so that's good to hear.
Overall, despite kinks (there are always some tradeoffs) Tidal feels like a no-brainer for any audiophile. Frankly, if one is an audiophile and cares about quality I can't really see how Spotify could be a consideration anymore. I feel a bit foolish not to have switched from Spotify to Tidal earlier.