Well, I've worked in tool and die and machining most my life and am very much aware why companies do things the way they do. I agree with you that in most cases in a highly competitive market, streamlining, cost cutting and and simplification or outright removal of processes are the motivation for changes. If the company produces a product that is equal to or better than what preceded it, then the customer also reaps the benefits in a better value product for the money they spend. I personally think CZ managed this with my rifle at least. Fit and finish is far better than any of the 452's I've seen.
The issue with the bolt lug change to a single lug is really a non issue. The idea is to get enough strength in lock up to do the job and also center the bolt face recess concentrically with the bore. This is more reliant on bolt OD vs receiver ID fit than any number of lugs or configuration of lugs in a bolt action.
I am not sure about the magazine issues if there are any. The 455 has an insert behind the mag that is removed for the longer ammunition and the insert does not interfere with the reliability or feeding of regular LR cartridges. The key to success with interchangeable barrels designed like the 455's is a very snug slip fit. I have to give a really good twist and pull on mine to get it out. This generally means hand fitting and selective matching at the factory. It is one of the reasons that purchasing the barrels in a fitted set is desirable as opposed to buying separately. Alternatively CZ could also sell slightly oversized barrels ( a few tenths over) that can be hand fitted by the owner much like many of the better 10/22 barrels out there.
A fully floated barrel also is not effected by a front sling attachment and is not susceptable to fluctations of accuracy from varying torques on a front lug or pressure on the forestock. Having a second screw in the action instead of out front also simplifies proper bedding of the action and provides a more stable base in the bedding.
In the end, if the average 455 owner can shoot as tight or betted groups as a 452, and have the option of having a different caliber rifle in the same configuration for only $139, the new 455 is a winner. I'm pretty confident that this will bear out, especially if the other 455's are make as well as mine was.
