I had a chance to spend an hour with V5 Pro today. I use a Kawai VPC1 as the weighted controller and a modified Bluthner instrument in PianoTeq.
I noticed the difference as soon as I started playing as it took on a new resonance and body. They are SO close to the real thing it is getting scary. It is Very responsive with my controller. I have not spent much time tweaking things other than creating the modified Bluthner I use. The ssd space required is crazy small. (MB's vs. GB's)
Besides the improved sound I like the convenience of being able to run it stand alone and have the built-in metronome and midi recorder to capture any spontaneous ideas. Works as a midi player also. It supports all 3 pedals.
I thought V4.5 was cool as it was Very responsive but did not have that body/string resonance (kinda muffled) I really wanted to hear so I would mix in a little sampled piano with it but this required me to turn everything on and run it in a DAW.
So far I am really liking it and am looking forward to spending more time just playing around tweaking some things as time permits. Even if it would have cost me for the upgrade I would have gladly paid it. YMMV.
Kind regards,
Rick