Very Well. I own a Swaro 65 and the Nikon ED. 50. The Nikon is no Swaro, but images are very clear at 40X (I have a 13-40x zoom eyepiece rather than just the normal 13-30x)
In fact I am thinking of selling my 65mm and obtaining an 80 because there is not a huge amount of difference between the clarity of the Nikon and the Swaro. I'll keep the 80 in the truck and take the Nikon in the pack instead of the heavier Swaro.
The Nikon is truly the perfect backpack scope. With the 40X it weight about 19-21 oz. It does the job in the field very well. I do not feel undergunned with it and I think most are shocked with clarity. Low light is better in the Swaro, but that is to be expected, but the Nikon still does very well at dawn and dusk.
If you can purchase the scope and the eyepiece separately that is the way to go. The Nikon 13-30 is still a great buy, but it is really worth it to get the 40x zoom eyepiece.
If you live local you are welcome to meet at Cabelas and Check it out if you want.