Disclaimer 1: The manufacturer provided me free samples of the 0.22uF Rike Capacitors that the following review is about.
Disclaimer 2: This is what I felt in my system, with my music preferences, with my aural tastes. YMMV.
A while ago, I decided to give my VTL ST-150 an overhaul to ensure good functionality. I replaced all the coupling caps and I started with the 0.68uF caps between the output tubes. That definitely gave me an improvement in most areas, but made the system just a touch bright. Once they settled in, though .
After I let them settle in a bit, I decided to tackle the 0.22uF coupling caps in the input circuitry of the amp. I contacted Rike to ask them for the contact information to dealer in the US. They were very helpful since there wasn't a dealer at the time, and were very prompt and kind in sending me free samples to try. It had been a long time since they shipped them to me, but it took me a while to get them into the amp. It's been a while since they've been running in the amp and longer still for me to find time to sit down and write this, but they're excellent capacitors.
I do not have the vast array of experience that some other members have here, but I'm comparing it to what I heard with the amp I got.
Short version: This brought back a degree of realism to music playback that I didn't think possible. It transported me back to a concert that I'd just been to a few days back. It made me feel the same exhilaration that I felt when I was listening to live music.
Longish version: Almost every rock concert I go to, I take ear plugs with me. This is usually because the sound is so insanely amplified and the sound so bright (Ozzy especially comes to mind), I have to put ear plugs in to be able to tolerate a whole concert. However, this particular Steven Wilson concert that I went to in LA was so well done, that I didn't need earplugs! They had the sound just right and I very much enjoyed the concert. As many of us do, I craved that same feeling of excitement listening to live music when listening at home. Things sounded good, but I wanted better. With the Rike in, I get that feeling of being back at a live concert. These capacitors don't highlight any part of the spectrum. They simply let the music flow very naturally. The bass is very textured and natural (and this was the part that got to me!). I could feel it in my chest and feet! The mid-range and highs flow so naturally and sound exactly like what I heard at the concert. No particular frequency band "shouting" at me and grabbing my attention. Dynamics are jump in your seat good. Separation of instruments is really good, and soundstage is excellent too if the recording allows it. If you can't tell, I really, really like these caps. While capacitors alone don't make the system, I think these caps allowed my system to really shine. The Rikes allow the music to get very, very close to the real deal.
Even my wife that doesn't get my craziness came by and asked what I'd done - the music sounds so much more, natural, live etc.
Rest of my system: Magnepan 1.7, deHavilland Ultraverve 3, Decware ZP3 phono, Kenwood KD-770 with Clearaudio cart