I know the OP has made a purchase, but for anyone else looking into this.
I picked a 457 Pro Varmint last weekend. It’s a step above the 455 Varmint that I had previously. I’ll be upfront and say I never thought my 455 was a quality example of the line, the trigger was fine but not outstanding, the bolt was gritty and it just never really shot all that well. I share this as any negative comments I’ll make on the 455 are specific to mine.
The 457 has the best rimfire trigger I’ve touched and I have more than a few rimfires in varying degrees of modification. For my use I have it set to 2.25 lbs and no pretrvale or over travel. It’s just a solid and clean break. It can be set lighter or heavier, I’m not set in 2.25 and may lighten it a bit more.
The bolt is much easier to run, this partly because this one is smoother than my 455 but mostly the new shorter action and the 60 degree throw are a delight.
I got it to the range last night, it’s still cold here in Indiana so I was limited to 25 yards at my indoor range. The first 5 shots, using Federal Champion, landed with 4 in one large hole and 1 flyer. CCI SV put 4 in a medium hole with 1 flyer. Eley Target put 3 in one hole and 2 that were overlapping the hole. I’m by no means an expert shooter and I tend to get excited when the first 4 go well and then pull the 5th. The performance I saw was because of the rifle, in a real rest (I used my range bag as a make do rest) it would have done much better.
I would say the 457 is worth looking at closer for those that are thinking of one. I bought this as the chance for CZ to redeem themselves, regarding rimfire rifles, for me. I think this one will be a favorite.