I think it is really dependent on the work you do. Reamers cost 10-20x the price of a drill, so you don't buy them unless you need them or have money to blow IMO. For general purpose use, I think a 0.001" press and 0.001" clearance cover most shop press fits and slip fits. I'm thinking of dowel pins and stuff like that. That is why I got myself an import over/under set for $100. Maybe if you like to have super pretty holes on nominal diameters then a fractional set would be worth it. If you have specific tolerances you need to hit (say -0.0003") then you'll need to source a reamer specifically to do that.
Remember, reamers make round holes with accurate diameters and good circularity, but not necessarily straight holes. To get a straight and accurate hole, it often pays to Drill -> Bore -> Ream.
Adjustable reamers also exist. They require a through hole since they have a fair length at the end of the tool that cannot cut, AND they take some trial and error to set the right diameter, but once they're dialed in, you can use them to accurately ream a whole bunch of through holes at an accurate and arbitrary diameter.
It's getting to be that time of year again .