I'll contribute my .02... I only started shooting LR 2 years ago, have only shot out to 1k or so, so I am no expert.

My first rifle came with a 6-20x40 Leupold VXIII, a very nice scope but had 2 drawbacks. First was the reticle (varmint hunters) a good reticle for varmints, but not great for real LR shooting. Second was the eye relief. It was tough to get it right, I kept getting a lot of scope shadow and was a strain on the eyes for long periods.

I was originally looking at Viper PST's, SWFA and Nightforce. The PST's were always out of stock/back-ordered. The Nightforce's are very nice, but to get a 20x FFP mil/mil it would be around $2k (although they can be had for just over $1k for the 3-15x SFP demo's at Mile High Shooting Supply!). A member here let me check out his SWFA and I did like it. He also let me check out a very nice IOR Valdada (check this http://tinyurl.com/6qwwhr2)

I just traded my Leupold into SWFA for $600/credit and bought the SWFA 50-20x50 HD (on sale) and so far so good! It is heavy, but so is the rifle... The glass is very clear and the reticle is good for me, no regrets so far. Their warranty/customer service is awesome too. I just picked up a SWFA 10x mil/mil (same reticle) for a trainer rifle.

With all that being said...
My shooting partner picked up his LR rifle 2 years ago also, (but grew up shooting and served in the Army) He bought a Vortex Crossfire 6-20x50 for $175+/-. The first Scope failed right away. He call Vortex and they sent him a new one in 4 days no questions asked. With the replacement scope he zero'd at 100 yards, then zero'd his turrets. We then shot out to a 10" gong at just over a 1k yards. After that he dialed back to zero and hit a perfect on bullseye on paper at 100y again. Next trip he confirmed zero at 100y, dialed to 1k and hit with the 5 shot. Then back to 100 before we left.

Ultimately I thing the shooter is the most important part. Glass is nice, but not necessarily everything. Shoot me a PM if you want to come by and check out my scope.