Who is using Firebird SQL?
Case Studies & Testimonials
Firebird is used and relied on by many user of different fields of business from all over the world because it delivers what it claims
It is known, from reputable enterprise survey, that Firebird is running on hundreds of thousands of productions sites around the world.
Public Listed & Prominent Users
It is also well known that Firebird is the database engine that drives SQL Account and SQL Payroll software. There are now over 250,000 companies using SQL Account and SQL Payroll
Go Behind The Facts and Figures
While it is interesting to look at data such as the ranking of database engines, we definitely won't referred to it as fact. This is because looking at ranking alone says very little about the features, performance, security and potential of a database engines like Firebird.
Mircrosoft SQL Server
Here are some amazing facts that you may not know about Firebird
Bigger is Better
Firebird (FB) max DB size is unlimited, max table is 32TB. Where else Microsoft SQL Server Compact Embedded Database (better know as SQL Server Express) max DB size is 10GB (4GB is v2008). 
Freedom is Good. End of Support is Bad
Firebird open source freedom is guarantee.  SQL Server Express can be continue, discontinue, file size reduced or feature restricted depends on Microsoft interest. Microsoft has discontinue or end support on many products. Example 1, Windows Server 2012 foundation (refer to page 1) Example 2, Windows XP (7).