Well, I left it a day before posting my first impressions, basically because it grabbed me

First session was four hours followed by a five hour, through-the-night settling into it all.
The game will be very familiar to any who played DI. With minimal differences in the visual style, controls and menu you can fit right back in there. I know that a few wanted a change, probably because other games do so, often quite radically - yet I think Deep Silver are saving it all for the next title. This one is a continuation and it is buying them time for the big one, hopefully
Dead World where we'll probably get a completely different game with new characters and scenarios all ready for a next-gen release.
Back to DI:R. It's a lot smoother in combat, difficulty has been balanced to a more realistic level and there are a load of fun new weapons to try out - some with really fun names. The amount of zombies has also been racked up - they still respawn very quickly, though not to the full amount if you are still in the same area. They are every fifty metres or so across a very dense map. So far I've only progressed across about two-thirds of the first one but it has so much to explore

and variety too - it's plenty fun.
So, without venturing into spoiler territory, the four original characters and a new one, John Morgan end up after the storm on another island in the archipelago. The infection is everywhere and the military have it contained from the outside.
So it's basically another find-a-way-off-the-island gig. The difference is that there are a few defence-hub missions and what are called the Dead Zones to contend with: places where the outbreak has been contained to and isolated. Unlike the quarantine zone in Moresby, these are arena-like areas, each different and less of a threat to the player if you wander too close.
As has been mentioned earlier in the thread, characters from DI can be imported at whatever level they were at, ot started afresh at level 14.
The NPCs you meet are survivors, mostly situated in the hub-defence places. A number of them can be traded with and seem to carry the same weapons and consumables each time you visit them, which is handy as in DI you needed to keep going back until the items you wanted cycled back up.
These survivors also have side missions for you to do, just like in DI and there is always one person per hub that can store any items you want to keep but have no room for. All in all the game is an improvement across all fronts. I can see me losing another three hundred or so hours on this game over the next year...maybe more.
Lastly, as the UK got this release last of all, anyone who has bought the pre-order survivor's pack with the BBQ sword will probably know this already. You will need to enter the activation code before starting the game, as you get this weapon and its mod blueprint given to you at the start of chapter 2. If you have not already done this, the BBQ sword will not appear until the next playthrough. Of course, if you restart your character or begin another, it will be there for them.
Have fun out there and remeber, it's a dangerous place.
EDIT: Oh, I almost forgot to mention the somewhat psychotic sounding elephant noises which all add to the atmosphere. There are other
altered animal sounds there too, but I can't really identify those as yet.
Additional info: confirmed that any imported character will not have their weapons or blueprints with them. Presumably these get taken from them by the armed forces.