It's not bad or anything, it's just really short. Took me less than 2 hours to beat. Pretty easy and you don't even get nearly as interesting of an arsenal as you do in the base game, let alone Opposing Force.

Apparently this was originally intended to be a part of the Dreamcast version of Half-Life which was cancelled, so I guess that explains why this feels a bit like an afterthought. Still worth a playthrough at least, if only because of its incredibly short length.