When I was researching before I bought a new spotting scope, I found that the HD glass doesn't make the picture any brighter in low light. It controls chromatic aberration and will make the picture sharper. I believe chromatic aberration mainly becomes a problem if you are digiscoping. If you want to learn a lot about optics, go to one of the bird watchers forums(birdforum.net). My buddy has a Swarovski spotting scope non-HD and it is an awesome spotting scope. I ended up going with a Pentax PF80-ED. With the 20-60 eyepiece, it cost me just over $1000. Added in a tripod and a pistol grip head and total cost was still less than a non-HD Swarovski. Setting my Pentax PF80-ED up next to his Swarovski STS 80, there is no discernible difference in view. Sorry, I know you only asked about Swarovski, but that's how I started and after a lot of research, I ended up with a Pentax. Can't go wrong either way!