.NET as programming lang maybe isn't bad (never tried) but installing .NET libraries are hell, and damaged several ppl OSes so far. The last version NOT causing troubles was 2.0
And about that unknown app:
first thing that is making me worried - its the website. One ugly header, 3 lines of text and download button. Much sities for trojans etc are looking like that. I know there is no need to make dedicated website for such thing but.. Or you can give at least one screenshot or something..
second thing - the size (okay, i know you cant do anything about) - small exe's files are mostly trojans. but good website will make me worry less.