I've been riding a Surly Straggler for over 2 years now, and for me the fat tyre gravel/cx thing is pretty perfect, but that's essentially what it comes down to: what do you want it for?
Mine's basically a ~200km a week commuter, loaded with my clothes/lunch for work for most of that, commuting mostly on bike paths that are either poorly maintained concrete/bitumen or gravel. On weekends I usually go on longer gravel/bike path/backroad rides. Basically it spends a most of its time offroad.
A mate of mine has a Rove ST which is very similar to the Straggler, with a bit less versatility built into the frame, and not quite as heavy-duty tubeset. I think most of the weight in the stock bike there really is in the wheel/tyre combo, you can probably drop 0.5-1kg there by changing to lighter 40c tyres or dropping down to something like 28c tyre. I think if you've got good bike paths and aren't going to be spending much time offroad, a Rove, '16/'17 Roadhouse or '17 Wheelhouse with 28c tyres would be perfect, but if you're wanting to load up and/or spend more time on poor surfaces, stick with ~40c tyres and more toward the Rove end of the spectrum.
As for fat tyres, I'm loving them. But again, a lot of that comes down to what you use it for. I can keep up with mates on carbon roadies on hilly road jaunts, no doubt I'm working a bit harder for it, but I'm also generally rolling more comfortably. There's a lot of good info by fat tyre advocates like
Jan Heine and the guys at
Silca that show a lot of benefits of fat tyres, but it still pays to adjust tyre size to intended use, it's not simply a "bigger is better" thing.
Probably my only disappointment with fat tyres has been the durability, I'm struggling to get more than 3,500-4,000km out of a set of tyres!
