In my Windows 7 desktop, mRemoteNG easily took more than 10 seconds to launch.
After bearing with this slow startup for some time, I finally decided to find the workaround or a fix to this problem.
A quick Google leads to the mRemoteNG forum and indeed, there are also others facing similar issue and a workaround is provided.
The solution is to add the following lines of code to the end of mRemoteNG.exe.config file located in C:\Program Files (x86)\mRemoteNG or in the directory where mRemoteNG.exe is installed:
Refer to the screenshot below: