I have older Bowflex 1090's. Currently living in the hallway because I got a new exercise bike and they were displaced from my office.
(They're also on wheels, and my hexes - which only go to 35 - are not)
The resolution really is 5 lbs. I suppose theoretically you could set one side to, say 40 and the other to 45 and get 42.5... but they're gonna be awkward that way.
IMO, they're too big for the lighter weights (hence I still have the Hex's) because you'll want to get them in closer to you than you can really do with the big diameter they have.
They are also far more delicate than a normal, non-adjustable... but I feel like that's true of all the adjustables. Don't drop 'em.
All in all, I like them for what they are. I suppose I could use them for everything, but I do use the hexes for lighter work.... that's also because while they adjust quickly, they have to go back on the stand, and it's not as quick as just putting them down and picking up another set of dumbells.
I'll generally adjust my reps to minimize changes on the bowflexes... So maybe I'd rather do 2 more reps at 80 than I'd 'ideally' do at 90... because some other exercise in the set I should really do at 80.
At least when I got mine, the only other real option was the Powerblocks. I couldn't find the big ones locally, but the smaller ones seemed awkward, which is why I went bowflex. (I similarly couldn't find the 1090's local, but the 552's were everywhere)
Ok... time for the aforementioned exercise bike.