Howdy, Neighbor!...
I live in Mckinney as well. Although I never get out to shoot anymore. I work nights and a lot of weekends.
However, on the rare occasions that I do get out, I generally go to the Billiard Den. This is the best room in the area, IMHO. Let me qualify that by saying that I have not tried any of the rooms in Denton or Sherman. The Billiard Den has good equipment, nice staff, nice patrons, and affordable prices. I don't gamble much ('cuz I suck), but there seems to be plenty of action there because I have never been in the place without someone asking me to play some. The Billiard Den is located on Arapaho road in Richardson, just west of 75 (Central Expressway). It's kind of hidden back in a strip shopping center. Look for it on the right just as you complete an S-turn in the road (which I think is just past Custer road).
The closest place I have found to Mckinney is the Main Event, located at 75 & Spring Creek Pkwy (stay on the service road after exiting @ Spring Creek). This is a teeny-bopper hangout that has some decent pool tables, but also has a bowling alley, laser tag, and loud music. No action here, but if you just need a close place to knock some balls around, it will do in a pinch.
There is also a Fox & Hound in Richardson at Campbell & 75. This has nice equipment, but is a little too yuppie (and pricey) for my taste. As another poster mentioned before, this is more a sports bar than a pool room.
Wizards, which someone else mentioned, is also a good place. It too is rather yuppie, or used to be. I haven't been there in a while.
If you drive back into Dallas, there are plenty of rooms around. Just do a google search. Good Luck!