Whilst investigating the process for schools to extract data from their existing library systems in order to migrate to Koha I have been surprised at the attitude of most vendors. All vendors of the propriety systems I have dealt with so far either charge many hundreds of dollars to extract records or make it difficult to get access; none provide a utility for users to export their records. They seem to forget the data belongs to the library not the container it resides in.
After the purchase cost of borrower items, cataloging is often the next largest expense. A school has a large investment in their catalogue records. These records form the backbone of their library and are a valuable asset; an asset they own, not the library system.
I am happy to say Koha allows the user to export all their data in a variety of formats, at any time and at no cost.
I believe a library should continue using their management system because it meets their needs not because it is too difficult or expensive to get their data out of it.
When choosing a library management system it is wise to ask how easy and/or costly it is to extract your valuable records should you wish to change in the future.