/proc

Nobody seems to like /proc
The API is ugly (though improved)
Many implementations are buggy
No user-side standards
Highly inconsistent formats
Format changes break applications
ASCII generation/parsing is inefficient

Proposals for changes abound
Rusty Russell:
Very simple API
One value per file
Al Viro:
Make it easy to export large tables
seq_printf and friends
Others:
Contents in binary or XML, or with BNF