This is the problem with this psedo-multiplatform solutions.
The delay on my machine was about 30 seconds at startup, then 20-30 seconds everytime I open the TOOLS menu to choose a port.
Now, with the fixed library, its barely noticeable (0.1 sec or less).
I was using the windows console to upload the sketches because this delay (I often use Bluetooth so disabling it every time I use arduino was a worse solution than using the console), even I am thinking on code a C# new arduino IDE, but until this moment I haven't found a free richtextbox component with visual studio-kinda capabilities, collapsible sourcecode, intellisense, etc.
I'm very happy with the results anyway, even when the creator of that library was aware of this error. (now a lot of projects using rxtx will be updated with the version 2.2 of this library thanks to this small research)
Knowing the port would help (this way you did not need to scan those bt-related laggy ones), but the way arduino IDE is, its necessary to scan all ports to show the TOOLS/SERIAL PORT submenu