Owned a couple of the 0.95 50mm speedmasters - one on Sony, one on RF.
I sold both.
That said: they're a little soft wide open when focusing close (but acceptable sharpness at medium to far focus), with noticeable CA. Bokeh is usually good, but due to CA, if you have a background with alternating dark and light (like tree branches against bright sky), it can look pretty 'busy' and unpleasant. They might be 0.95 from the bokeh perspective, but let a little less light in than you'd expect with comparatively poor transmission and wide incidence angle on the sensor.
Build quality felt sturdy and solid in both cases, with all metal construction. they were also surprisingly heavy for the size because of this.
The manual focus at .95 made focusing pretty hard, but that's a lot better on cameras like the r/rp, which pretty good manual focus aids.
I found them useful on wider scenes to isolate the subject from the background in busy environments; creating a few unique shots. Still, even then, focus was tough, but those shots where I got it right I really liked. The problem was there were a lot more shots that I missed where I got it wrong
In the end, the last one I owned on RF I traded in to get the RF 50mm 1.2 instead. Half a stop less bokeh, but an autofocus that nailed it every time. Of course, 3 times as expensive, soooo.....
I'm not sure how different the optics are on this one though, since it's for EF mount, rather than mirrorless.
Short version: If you like manual focus lenses, then this is actually a pretty decent option, though a little tricky. Otherwise if you're more like me, stick to something with autofocus where you'll end up with a LOT more keepers rather than mostly 'man, this shot would have been SO good if I hadn't missed the focus by half an inch'