A few thoughts:
1. Measurement mics are omni directional; something that our ears are not.
2. You can use multiple mics for measurement. Capsules will cause variations, so purchasing a mic with a calibration file is helpful. Please note that a capsules' frequency response will change over time, this is true even of expensive measurement mics that cost thousands. However with a functioning mic this is not a huge deal as the frequency variation which occurs in a room is much more significant. If you take a measurement, and then move that same mic over an inch, this usually causes a greater variance than between most functional measurement mics model/capsule differences. To the point your two ears never hear the same thing, and your brain is quite good at compensating for this.
3. If you are doing something such as time aligning you want a single measurement.
4. If you are doing general measurements to see what a loudspeaker is doing frequency wise in a given area than more measurement will give you a more accurate picture of what is going on. In a Rational Acoustics training I attended (the makers of Smaart) Jamie Anderson recounted that there is a diminishing return to multiple measurements. They performed a test in a venue where they collected 60 measurements in each area, and then averaged them. They kept dwindling down how measurements were used. 30 down to 20 and so on. The result of the testing was that: Two measurements is far superior to one, and that three measurements is better than two. Roughly though this is where the point of diminishing returns hit hard; the data given by three measurements and sixty were not significantly different.
5. Multi mic setups are all about speed, and potentially at the expense of accuracy, due to capsule variations. In live sound sometimes you get 20 minutes to do your measurements and tuning. My personal measurement rig is 3 mics, on a folding 4ft Manfrotto stand, with Triad & Orbit clips with a Cat Rat breakout and a 150ft tactical Ethercon (all 3 mics analog over 1 cable). It works great for large venues and moving quick; but I wouldn't bother with more than a single mic for home; where I presume you value accuracy over speed.
6. Measurements are not pretty to look at. Real-world "flat" is a far cry from what one would hope. A common response is to try and EQ every peak/dip. Jamie Anderson refers to this as "measurebation," and it does tend to sound a lot like comb filtering. What is prescriptive and corrective EQ for a dip in one area, might be a null an inch or a foot over. What is corrective in place is destructive in another; which is a general principle in audio, everything is a tradeoff. This is why averaging many different positions is important. In the live sound land (different from at home) the most skilled tuners tend to do 3-4 wide-Q filters at most. It is also important to realize that EQ is a hammer, it is not the correct tool to fix everything; it cannot fix room problems. I still do think it is quite useful, I do use Sonarworks on both of my main systems, but it is not a replacement for room treatment either.
Hopefully that helps you out