My first machine was a TRS-80 Color Computer 2 with a cassette tape drive; compared to the PET, due to the "generation difference" (probably in the encoding method?) - plus Radio Shack - it's cassette storage was actually really reliable.
People are still pulling old software and data off of some of their old CoCo tapes, what little problems there are typically can be solved by dumping to digital file and editing in some audio software to clean things up.
My first computer was a TRS-80 Model I. The cassette tape storage was just Radio Shack's regular tape recorder. For some reason you had to use different volume settings for BASIC and machine language programs. The volume setting was horribly imprecise and I was always having to reload programs. The Commodore 64's tape recorder was a big upgrade.
Every time I turned the power off or wanted to try a different program I had to start from scratch.