My experience (having had the P30 for about 6 months and now the P30+ for about a month) is that noise has been reduced at higher ISOs, the screen is better, and it does shoot marginally faster. I haven't noticed any substantial differences in color rendition, but that's OK as I found the colors on the original P30 to be quite nice. I don't shoot product or color critical work, though; for portraits, landscapes and the like, the color is subjective anyway. The original P30 met my subjective color rendition criteria, as does the P30+.
Shooting speed with the P30 never bothered me, so that hasn't been a big change. Having a useable ISO 400 and a useable screen IS a big difference.
Oh, and Live View is totally irrelevant to me, so that wasn't a consideration.
I obviously thought these differences were worth getting the P30+ since I got it. But the price difference at the time wasn't that big; maybe $2000? If we're talking about a much larger price difference, I don't know if I would go for the Plus or not.
I will be using the P30+ this weekend for some pretty intensive outdoor shooting at a variety of ISOs, so I'll have more impressions then.