My biggest concerns with the PS4 is OS interface, UI controls, clunky OS systems (Vita management is really really weird to me), Store issues (Vita store is fast, but also really buggy for me sometimes), and Online system in general.
I don't trust sony at all with UI for anything more than the initial year. The XMB was great for that first amount of time, but the more stuff you add to it the weirder and less useful it got. The Vita was fast, but the bubble/page system was horrible to manage. If you have a lot of content, it becomes much less intuitive.
With my relatively little time with the 360, I've been impressed with the UI of the latest dashboard. I'm generally looking forward to the Xbone interface more because of this, but that might be misplaced enthusiasm because I really haven't used the 360 nearly as much as the ps3 (and therefore have much less content on it). I also work on the WP team, and really like the UI and flow of the OS...so maybe I'm just Bias for metro's blocky interface. The PS4 seems to be going that route, but I haven't actually seen a good video of someone using it with controller in hand. Just marketing videos--which I really don't trust at all. My relative excitement and glass half-full nature is because I've seen the OS used and can relate to using the Kinect with it. I've already got many situations where the Xbone OS is going to be really nice for me--though other people seem to not have the same interests/use-cases as me, big surprise
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
. The PS4's OS/Interface on the other hand is just this big black box. I can't be excited for it if I haven't seen it--right now it just seems like a souped up PS3 with some social feeds mixed in.
Sony's PSN has gotten way better over the years, but my little interaction with XBL has shown me how bad by comparison it is. With the paywall in place, I imagine they'll be able to bump up the download speeds and make their internet infrastructure better, even if it takes 6 months or so. Patching offline with PS+ this past year made playing games on my PS3 fun again...rather than having to wait for another update nearly everytime I booted the system. Whether XBL will offer more innovative features again this gen, they haven't proven it to me, so they'll probably be closer this gen. I do like the 'queued matchmaking' feature though, and will probably use that quite a bit.
I can't wait for November to get my grubby hands on both systems and futz around with the OSes/Applications/Capabilities that they offer. Really intrigued about this next step for consoles. WiiU didn't do much for me, but its serviceable. That console is basically going to be a Nintendo box for me, so I don't really care too much.