I have been using Java for 3 years for my telecommunication projects, which relies mostly in Web services, but for desktop applications I prefer FPC/Lazarus.
If you compare big desktop projects written in FPC/Lazarus with big desktop application that written in Java, for example Lazarus itself and NetBeans, FPC/Lazarus developed application will be more faster, light, and consumes less resources. In my Core 2 Due laptop, NetBeans needs about 25 seconds to start, if you close it and start it again, it needs about 15 seconds, while Lazarus needs only about 4 seconds in the same machine. For memory consumption, NetBeans and it's Java virtual machine consumes about 600 Megabytes of RAM, while Lazarus consumes only 37 Megabytes. I have been using NetBeans since version 7.1, and now I'm using version 8, there is a noticeable delay in every new version of it, while Lazarus IDE is still hold the same speed, .Net/C# desktop applications are even worse, VS (I assume it has been written using C#) make me think my laptop is crap and I should threw it.
In my opinion and depending on that comparison FPC/Lazarus is good choice for large desktop applications.