Simple and easy to understand, but:

• No real data structures, just multidimensional arrays and lists
• No nested structures, variable-length types, or ragged arrays
• Only one shared unlimited dimension for appending new data
• A flat name space for dimensions and variables
• Character arrays rather than "real" strings
• A small set of numeric types

Corresponding classic netCDF format has performance limitations:

• Large variables must be less than 4 GB (per record)
• No real compression supported, just scale/offset packing
• Changing a file schema (the logical structure of the file) may be very inefficient
• I/O is serial in Unidata netCDF-3 (but see Argonne/Northwestern Parallel netCDF project)
• Efficient access requires data for a variable to be written and read contiguously

Despite these limitations, netCDF-3 is very widely used in climate modeling, ocean science, and atmospheric science, and has been used to represent some very complex data, e.g. grids described in Gridspec specification.

2012 Unidata NetCDF Workshop > The NetCDF Classic Data Model