Nothing wrong with the 6.5 calibers. The Scandinavians have been killing moose with the 6.5 x 55 for over a century. The recent players, 260 Rem and 6.5 Creedmore, are just a reinvention of the wheel based on the 308 Winchester.
What probably hurts the Swede is the fact that many of the older actions are not as strong as the later Mauser 98s and so pressures should be kept lower. That and the fact that the case is an original design, not based on anything else.
There have been some pretty good deals on 6.5 CM rifles. A hunting friend bought a Savage Axis 2 years ago that cost him around $250 after a rebate. That's a heck of a price for a good entry level deer rifle. and it shoots great with factory ammo.
I'm surprised that nobody mentioned the 264 Win Mag, the perfect 6.5 for those who need to compensate for their shortcomings. A little short on barrel life but it's right up there with the 7mm rem Mag for long range plains and mountain shooting and recoil whackability.
The one thing about the 6.5 cartridges is the sectional density of the bullets give great long range accuracy and awesome penetration, regardless of bullet weight. The caliber just seems to be in that sweet spot design wise.
John