How long do you plan on keeping the 928? That might factor into your decision. This phone has been on the market for about 14-16 months? Will it get firmware updates in another year or so? Maybe, but I doubt it.
While performance has been good, I've noticed mine has dropped slightly with 8.1. Screen animations are jerky and apps start more slowly and sometimes feel a little sluggish. For example, the start screen tile animations are noticeably jerky it times. It was really bad with initial 8.1 release, but got considerably better with the updates Microsoft released. I don't yet have Cyan firmware, so I'm hoping that brings it back to the pre-8.1 performance. I can live with it at this point, but I think Microsoft Mobile should be working to get it back to the pre-8.1 level since most phones have at least a two year life.
It is a very good phone. Battery life is excellent--was before 8.1 and then after 8.1 once we got those updates. It sucked on the original 8.1 release. I easily get 12-14 hours on heavy use days and better than a day with light use. Phone call quality is great. Camera is awesome. Screen is beautiful and is very legible in daylight. I love the Clear Black display. Took me a while to appreciate it coming from the HTC 8X because text seemed a little blurry during scroll on the 928 compared to my 8X.
I really like getting the Nokia apps. Those really make Windows Phone shine and I hope they'll come to all handsets in the near future. You probably are already familiar with those since you have the 925, but just wanted to give you the perspective of someone who moved from a non-Nokia WP to the 928.
My screen does occasionally--maybe once every 2-3 months--stop responding to touch. I just restart the phone and it's all good. The screen also occasionally paints weird when I tap the power button to wake--like it's in 256 or 16 color mode. A quick off and on tap of the power button resolves that.
If I understand correctly, the 925 is lighter and thinner than the 925. Have you checked that in a store to see if the heft and girth of the 928 suits you? It is big, especially compared to the iPhone 5S my wife and daughter have. My wife makes that comment every time she picks up my phone. It isn't a huge deal for me, but I do sort of wish Microsoft Mobile would work to give us something a little thinner and lighter while retaining the great build and features we're getting from them. Might be mutually exclusive and I'll take the build and features over thin and light, but I suspect the heft hurts them a little with female buyers.
I've had my 928 a little more than a year now. Got it on contract since I was up for a new phone and this was before VZW offered the Edge plan. So still have a year to go on the contract. I've typically just purchased a new phone (all Windows phones) off contract halfway through my two year contract, but I've been pretty happy with my 928 and haven't had a huge itch to make the jump. I've been eyeing the ICON. It is nice. Would love the 1080p screen and 20MP camera. With kids, that higher res camera would come in handy for sports shots from the sidelines. Would also love a 1520 like phablet, so sort of been waiting to see if something like that materializes on VZW.