We have it running just fine on our 4.1.5 test board.
As for server load. As said in the installation instructions, i would strongly recommend to use the cms cache on that widget. It does resize and save a number of pictures when it does run, a process which can't be fast. But it doesn't have to do that often. Articles in the Slider most likely won't change for hours, on some sites even days - so a cache time of 60minutes or more shouldn't be an issue. Even 30minutes shouldn't stress your server at all.
Once it is beeing loaded out of the cache it is blazing fast and won't stress your server at all.
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