I've got a nice Anschutz sporter and was trying to work my way down to fewer .22s, but that 455 really has me tempted. The idea of an easily threaded/suppressed .22lr, .22Mag and .17HMR combo gun is very interesting.
From what I recall of seeing the 455 trigger assembly, it should be fairly easy to swap out the spring, and provided the sear engagement is smooth, you could probably get a very crisp pull. The few 452s I've used have certainly had useable sporting triggers.