I've been wearing 510's the last few years, they just fit me better than anything else out there, and they are relatively cheap, especially on sale. However, there are a few problems with regular 510's. The main problem is that the crotch wears out SO fast, especially if you bike commute, which I do, about 4 miles/day. After 5 or 6 months, you get a hole there, and it's ugly, and ruins an otherwise good pair of jeans. These have the crotch gusset, so they should last twice as long, and they feel pretty burly near the balls, I'm impressed.
On top of that, they are "waterproof." I wore them today in a light drizzle, and water beaded right up and rolled off. Nice feature. I'm sure it won't last long, but it's still pretty cool.
I don't care about the lock holder on the waist, or the reflective accents when you roll the cuffs, those are things that you don't see if you wear jeans without rolling and a belt. So it's cool.
They run true to size for 510's. I normally wear a 33x30, which they don't stock here, but the 32x30 is fine, a little snug, but still comfortable.
Overall, better than regular 510's, at not too much extra cost on sale. Will be purchasing more.