Past few weeks I've been shooting with a Kowa SE with 50mm 1.9 fixed lens. I also shoot with a Kowa 66 and super 66, have 5 lens. In terms of the 35mm, downfall is the leaf shutter and limited lens line up for the SET r, last of the breed that took interchangeable lens. The overall build quality is fair a for consumer grade camera, the meter is accurate, the lens is very good, 6 elements in 4 groups, sharp wide open, as good as any 50mm lens I've got. The leaf lens is problematic, very complex, hard to repair. To top it off there is a baffle to protect the film from light as the shutter has to be open to focus. Topcon made a similar entry level leaf shutter camera.
After 40 years or so finding Kowas in working order will be a challenge, were not as popular as say Pentax, Nikon, Canon or Minolta, and those that do survive will likely need to be worked on. I bought 3 before I got one that works, paid very little for them so one my working copy cost me around $70 and I have 2 for parts. Have not not gotten around to seeing what makes them tick, maybe over the summer.
In terms of Miranda, another brand I collected, the early models are rather sound, the EE, Senormate and the last body the Dx were not so good. Miranda was one of the first Japanese 35mm SLRs, the first the Oreran is very collectable. The weak point of the EE and Senromate was that the light meter is on the mirror, over the years the constant slapping up and down and something breaks. The lens are very good, the line up is average 25mm to 300. It has a dule lens mount, a bayonet and a 44mm screw mount. Longer lens were made, a 400 and a 800, not by Miranda, Soligor and others made these and were all preset. The Dx was as mess, drove AIC the parent company bankrupt.