Minor spoilers. (I think? Didn't watch the trailers or gameplay demos.)
Graphically it's an improvement from the last game, which is as to be expected from one being Xbox 360 and the other being on Xbox One. The the HUD feels almost identical to that of gears 3, with a few minor quick time events and some clean-up being notable exceptions.
Gameplay-wise, it's a gears game, with a couple of minor changes. The vaulting and cover system got a few minor tweaks. They cut a few of the weapons and added a few new ones, although I wasn't thrilled with many of their decisions.
Horde mode is fine; it's one of the biggest reasons I put money in the gears franchise, after the campaign anyway. The use of deploying things from a central location gives you more freedom then gears 3 did, making bases out of virtually anywhere, which I like a lot more than three's very static style.
As for online multiplayer, I don't think years has ever been a game that's actually focused heavily on its multiplayer matchmaking. A few minor balancing tweaks were made to the modes and such, but it has more similarities than differences with the other few games.
I think there's a lot more emphasis in customization, none of which that actually affects gameplay much, but enough to give you a little more personal flair with your character. I didn't mind it at all, especially since they added some new skins that weren't in the previous games, although it did feel like gears was trying to go to the microtransaction route of disappointment.
I was extremely disappointed with the campaign. The story felt hollow, especially for a gears game, and nothing interested me about any of the characters they introduced. JD isn't particularly interesting with the exception of the fact that he's Marcus' kid, and I have no idea if it was on purpose or not, but his motivations were anybody's guess. Del kinda just felt... There. Kait was probably the most interesting edition to the main cast, but even she felt one-sided and predictable.
On top of that, the level design is pretty lazy. I remember on at least three occasions to end the level all you did was backtrack your way through it. I guess it makes sense to do that, but I don't remember that ever happening in gears 3. Not to mention, there doesn't really seem to be a sense of urgency or world ending threat behind The campaign, which I think gears is famous for in the first place. It was extremely predictable, to the point where I didn't really feel anything for any of the main characters when it got to the conclusion. It felt like a rehash of subplots in the other gears games.
All in all, virtually everything besides the campaign, which is the part I was looking forward to the most, received some changes, although whether or not they were good or bad remains to be seen and it's kind of up to interpretation. It's a fun game to play and invest some hours in, although I wouldn't say it's necessarily as fun or entertaining as gears 3. It's a fun game, but in my view a terrible continuation to an impressive, decidedly rare story. 4-5/10, tops.