I've never owned the 710, but I've held one and studied it. I'm awaiting the arrival of my order of one and that's why I was reading this thread. A few years back, I owned a millie-S30V all black; probably produced in 05 or 06. I did like the knife. I did feel that the millie's tip would break in an instant if it was to meet any hard material in a thrust.
One night, being extremely hamered and night-hiking with a buddy (this explaining the ridiulous actions I'm about to explain), I decided to test my millie's "capabilities" on a small tree; aproximately 3 inches in diameter. Up to this point I had only carried my millie as a ready reserve defesive weapon and only used it for very, very minor slicing tasks. Anyhow, I hacked the tree down in a couple of swings with little effort. Afterwards I was astonished to find my mille had more bladeplay than something you would win at a county fair carnival game- not even an exaggeration. It was although the impact had just flat out destroyed the knife. Standing by a pond, I tossed my millie into it and vowed to never again buy a spyderco.
I've bough many Spydercos since then and regret not just sending that millie into syderco for a fix as I now contemplate buying another. I'll probably get the new Police-3 though because I love tend to trust the lockback over the liner-lock though I love Emersons and personally deem them as the best. I have learned since then some knives are just lemons and had problems with Benchmades as well and when you get a lemon, you just write the company; although Benchmade won't respond to three crap nitrous strykers in a row. The 710, only having held and studied it, feels very strong and posseses the Spirit of a born killer. Axis locks, IMHO, are the best short of fixed blade. The millie has a devasting blade as well and easier to sharpen, but it's too light and has the feel of a Glock as opposed to 1911 feel of the 710. Personal preference. I do trust Spyderco's quality control over Benchmade as I've only had one dissappointing Spyderco incident and three with Benchmade. I hate the millie clip. Benchmade G-10 is slick and although I actually prefer the feel, many others will not; especially if their hands are wet.
As far as S30V vs D2, there are no known S30V critics out there and those who despise D2 owe their distaste to imporoper blade maintinence and poor sharpening equipment. I personally have never had any problems with D2 rusting. I wipe my knives down periodically, before storage, and usually after use and every D2 bladed knife I have, came razor sharp and stayed that way, but with minimal use. I love S30V, D2, VG-10, 154cm, and ATS-34. I see too many criticisms of D2, VG-10, 154cm, and ATS-34 on here. They are good blade steels. Every steel has it's down-sides. S30V, which has been worshiped as a God as of late, chips like slate at times too. Back to the 710 and millie, they are both awesome knives, provided the factory isn't having a bad day, and they'll serve you wonderfully for the money.