I've been shooting a 6.5 WSM for about 3 weeks now. I only have about 250 rounds through it so I can't say much about barrel wear. I know that my throat hasn't advanced at all (last measurement was about 100 rounds ago). I've heard that the barrel will shoot out in 400 rounds and also move .001" per shot. I think these claims are made by people without first hand experience. I've shot it, I've measured it, I LOVE IT! I used the rifle to win our provincial F class championship. I only used it to shoot the 900 and 1000 yard stages, favoring my .260 for 3,5 and 600. I haven't shot for raw groups at long distance but based on my plotters from the match the round is effective. I am sure that it saved me a couple of times on a wind switch that I missed allowing me to hang in the V bull when I should have been blown out. At the present time I am shooting 65 gr. of H1000 with a moly coated 139 Lapua .010" into the lands, Fed 210M. I get 3175 FPS out of a 30" barrel. I know I could get it going quicker but the pressure is low and SD's are under 10 fps. Let me know your experiences if you go this route, I will post an update as I gather data.
I know of several fellows shooting a 6.5 based on the wsm and Rem SAUM case. I believe the Rem to be the more efficient case as it is a bit shorter and not so over bore. Of course everyone hates Rem brass so many shy away from this route. I have been told from several people including a ballistics technician from Sierra, that Winchester is bringing out the 6.5 WSM themselves. I'll wait until that happens, hopefully they shorten it up some.
Read the posts on Benchrest.com by gunsmiths and shooters who have built the 6.5 WSM, most concur greatly overcapacity and barrel burner! Most have recommended that the case be shortened by about .200 to .225. That seems to be recommendation at this point. Would recommend that you wait until dust clears unless you have about $1500 for reamers, barrels and dies and replacement barrel if it does not work out. Winchester right now has some real quality problems with brass. I shoot 1000 BR with 300 WSM. Seems you only find one of 4 cases that will work. Case heads all over the scale on thickness and size. Weight will vary by as much as 7-8 grains in one lot of 100 cases. Primer pockets are funnelled into the flash hole instead of being flat so you cannot uniform. No one makes a powder funnel that will fit the case, take blue bonanza and dremel tool slits in side to slide over case necks. RCBS makes a # 43 shellholder and Redding modified their #6 shellholder about 1-2 months ago to fit, but no markings to differentiate new from old. Even then found cases that will not fit in either. However once you get some cases it will shoot. We just had VA 1000 BR state championship and 300 WSM took 1st and 3rd in Heavy gun.