Copy on read doesn't even make sense, since a copy is a read.
Most problems people ascribe to reference counting have way more to do with excessive memory allocation and instead of fixing that problem and getting massive speedups of 7x or more, people try to fiddle with memory management schemes to gain 5% here or there at the expense of large unpredictable pauses.
Most problems people ascribe to reference counting have way more to do with excessive memory allocation and instead of fixing that problem and getting massive speedups of 7x or more, people try to fiddle with memory management schemes to gain 5% here or there at the expense of large unpredictable pauses.