It seems to me that scales can inspire varied reactions among coffee drinkers or even within one. In certain moods I'm of the school that weighing seems rather fussy. It is, after all, only coffee and if one is off by a little bit does the world not still go round? Notwithstanding, if one has a scale already, it's actually more fussy to *not* use it. Pushing a couple buttons is all it takes to start it, and eyeballing a measuring cup's miniscus strikes me as more difficult than reading a digital read-out.
I don't fret too much about scales when it comes to weighing beans. The advantages here are too obvious for me. Darker and lighter roasts will vary in density, and I've found that even a couple-gram difference will greatly affect the final result, especially for an individual mug of coffee.
Things are less clear when it comes to weighing water, especially for hand-pour, which is my preferred method nowadays (I'm partial to Hario's v60, named after its angle). If you measure water by volume before brewing, some negatives enter the equation. Besides inconsistency, the water will lose temperature more rapidly than it otherwise would (in general, not a good thing, especially for high-grown beans. There's a reason why Japanese gurus prefer low temperatures...) and the last bits in the kettle will pour erratically.
One answer is to put more water than you need in your kettle, place your brewing device on a scale, tare, and then just measure the total amount of water poured. This can work well.
Another answer is to go by flow-rate. A scale isn't required for this. One just keeps a slow steady flow and judges volume poured according to time. With practice it's pretty easy to be consistent and it's a fun exercise in concentration.
Flow-rate and total weight poured can of course be combined, if you really want consistently good brews.
If you want to buy a scale, there are a few things to consider. Are you just interested in weighing beans? In that case, a basic pocket scale should do.
I use a scale for more than just coffee, so I think something with higher capacity is preferable. I think it's worthwhile to go for an established brand: My Weigh or Jennings offer the best overall value. Ohaus is good but overpriced for what they offer. Whlie most scales are made in China nowadays, brand-names have better quality control. Most companies selling scales are not scale companies in the best sense...they don't design or test anything--they just buy scales from China and have their name stamped on them.
Sidenote: it's generally not advisable to weigh hot decanters directly on a scale, which I see a lot of shops do. Unless you have a lab scale with a thick stainless steel plate, you can very easily damage the scale's sensors.