as it is,if it fails,it just creates an empty package,which is pretty obvious to spot.
I test about every single package i ever build with this,makepkg or checkinstall.
The packages that i picked to test were hard to build and dont spit out obvious messages when there is something wrong at the end, only checkinstall dont wants to package them after configure and make went without saying much. I did it to see what will vpackager do with them.
As for the desktop files,I think it would be pretty simple to implement somehow in vpackager, its worth having- it is a pain to write proper .desktop files and link them with a proper xpm
...Maybe without autoresizing/converting,because that will have a imagemagick dependency.
But in any case, to add a desktop file,one must explodepkg,add the desktop file and the icon,and then makepkg it again.This changes user permisions over the directory where its done,so the user has to erase them as root later.
Most applications that are gui and need a desktop file,have a desktop file and an icon...but yet again-there are so many that dont.