From the link provided by Ben:
"Dark Urine Means Dehydration
Whether or not this statement is correct will depend on how dark the urine is, because the depth of color in urine will vary inversely with the urinary volume. Although the volume varies greatly among individuals, in our student laboratory (see above, under Other Data Since "8 × 8") the mean value was 1,520 ml/24 h (Table 3), with a mean urine osmolality of 590 mosmol/kgH2O. Both values are those generally cited as being "normal," namely, 1,500 ml/24 h and 600 mosmol/kgH2O, respectively (73, 92). At a urine osmolality ~600 mosmol/kgH2O, the concentration of solutes in the urine is such that the urine has a moderately yellow color, which might be interpreted as "dark," especially when contrasted against "pale yellow" or "clear," which is specified in most of the lay literature (26). Yet, at the above-cited normal urinary volume and osmolality, the plasma osmolality will be well within the normal range and nowhere near the values of 300 mosmol/kgH2O and higher, which are seen in meaningful dehydration. Therefore, the warning that dark urine reflects dehydration is alarmist and false in most instances."
My subjective feeling is that I've got a good sense of what normal urine color is for me and that I don't "go off the deep end" when there's some moderate yellow color. I can see and feel a difference when the urine is truly dark. I don't try to shoot for the (supposed) ideal of "normal volume, normal color, and normal frequency," but I do look for excessively dark color, unusually small volume, and odd sensation while urinating, and try to have a general idea of how often I'm peeing.
On the whole bottles vs. bladders thing, one advantage to a bottle is it's easy to monitor how much your drinking. I have to pull the bottle out anyway to drink, and I can visually determine how much water is left in the bottle. With a bladder, it's kind of a hassle to yank it out my pack and check the level, and stopping and pulling it out kind of defeats the whole convenience of using a bladder. I haven't ever had a Camelbak or a Platy leak on me, but I do consider a bottle more secure. I'd never take a Camelbak or Platy into my sleeping bag with me, but I do it all the time with a bottle.