My intial impression of the R-50 (after a few hours of listening) is that it's a bright iem that can be slightly sibilant. Detail is great, bass is tight but not extended and the mid range sounds very slightly recessed, it doesn't sound at all warm.
Unlike the Hifiman Re-262 I got at the same time the R-50 can be driven easily by my Clip Zip. Strangely unlike the Re-262 it doesn't appear to benefit from my Firestone Fireye Mini. I haven't tried a different amp yet.
Compared to the Etymotic HF2 (same as the HF5 with a mic) I find it less compelling. This might be because I like how HF2 handles the midrange which sounds more forward, open and detailed.
Other notes: I'm using stock tips that came with R-50 as the Sony hybrids I tried didn't seem any better. Build quality appears to be average though I can state I do not like the braided cord (gimmicky) and memory wire. Isolation with the stock tips isn't great though comfort is very good.
Additional listening with different tips (Comply usually works best for me in most cases) is required before I'll be able to more fully judge this IEM.