I'm very pleased with the accuracy of mine. I have the wood stock gun and it's easily shooting 1/2" 5 shot groups with my handload of Re-22, Nosler 115 BT, Wby brass, and Fed mag primers. I've only just loaded it to "standard" over all length also. Some folks are using 7mm Rem mag brass and forming it to 257 Wby, instead of buying the good Norma made Wby brand brass (due to the cost of the Wby brass). If you go this route, just be aware that the powder capacity of the Rem brass is different (less I believe), and plan accordingly during your load development.
The barrel heats up pretty fast while shooting, so watch your barrel temp. Recoil is about like a 270 win. Very easy to shoot from a bench with just a T-shirt on. I replaced the trigger on mine with a Timney almost straight away, what a difference a trigger makes. Yes I believe the Howa mount is exactly the same, I'm using the standard Leupold mount on mine and it's not a problem. The only negative thing I would say is I wish the gun was a little lighter in weight, 8 lbs is a bit heavy for a "standard sporter".
Overall, I would certainly do it again.