Limitations

•Although the editing of the attribute fields of most shapefile types is fully supported, the editing of geometry (locations) is supported only for 2D point shapefiles. This means that there's no support yet for drawing or editing polygon or polyline shapes. (For that I would suggest the free and highly-versatile Quantum GIS.) Two relatively uncommon shapefile types, Multipoint and Multipatch, are also not supported.

•A shapefile with memo field attributes is unlikely to be read properly by another GIS program, the reason being that ESRI's software has never supported them. (Some GIS viewers, but not  ArcView, will tolerate the presence of memo fields while simply ignoring the DBT file containing their data.) Many database programs, however, can read and write DBF files with memo fields, so they can be involved when information needs to be exchanged. When a point shapefile is exported, the geographical coordinates are easily included in the set of attributes, making the DBF component self-contained. WallsMap can export an Excel spreadsheet (type XLS) where the memos have been converted, possibly with truncation, to fixed-length text fields.

•Even when extended with memo fields, shapefiles are not as flexible as some proprietary GIS formats. Field names are restricted to 10 characters (one or more uppercase letters followed by digits or underscores). A fixed-length field can't store more than 254 characters. The record is limited to 255 fields with a maximum total length of 4000 characters. Neither the SHP component nor the DBF component can exceed 2 GB in size, which, for a  2D point shapefile, imposes a theoretical limit of about 76 million records. The DBT file that stores memo field data has a theoretical size limit of about 2 TB.

•Although you can have multiple instances of the program running at once, they can't have the same project (NTL file) open, nor can their projects contain the same shapefile layers unless the layers are set to be non-editable. The program enforces these restrictions.

•You are allowed to have multiple projects (layer sets), open in the same program instance; however, when two or more such projects share the same shapefile, editing of that shapefile will only be allowed in one of them, the one that first opened the shapefile as an editable layer. In the other projects the shapefile will only be displayable, but it will at least show the effects of any edits.