I think you get access to a few outfits, which make bugger all difference but you get the Patient Zero story. I'm going to try it out today and will let you know what I think.
One thing I would check out - download Hitman 2 and see if it recognises that you own Hitman 1. It may let you download the Hitman 1 levels inside Hitman 2 so that when your PS+ sub runs out, you could potentially keep playing with Hitman 2. I don't know if this would work 100% or not but it's worth a try. I've just had a look on the PS store and it seems their Hitman offering is a brand new SKU so the Hitman 2 unlock may not work. But as I say it'll only cost you time and bandwidth to try it.