I like Plano and the schools. We've also lived in Colorado and Maryland. Each time we've moved I've made the decision about which specific neighborhood based on school systems.
There are some great districts in the area - do your homework and make the decision based on what's important to YOU.
Check out the Texas Education Association website (http://www.tea.state.tx.us/). While you may be most concerned with elementary & middle today, you won't want to move to a different high school after your kid(s) have made a lot of friends. Consider the high school the schools feed into - educational and otherwise. In comparing Texas schools, you can check out their "Texas" rankings. But if you're comparing to other states (relatives or your personal experience) - compare SAT scores, since that test is consistent from state to state.
Check out the school websites, drive by the schools, and visit the schools. If a school is unwilling to schedule an appt with a prospective parent, I would take them off "the list".
My son attended one year of elementary school in Plano at Bethany, which was a good experience for us. He is now at Schimelpfenig. I've been satisfied with both experiences. The schools he attended in Maryland and Colorado were exemplary so my expectations are high. Some of the best school systems in DFW are Highland Park, Carroll (Southlake-Grapevine area) and Plano. Each has positives and negatives. I've also heard good things about Allen & Frisco. I really think in comparing Plano, Allen & Frisco, it comes down to preference. For example, Allen has 6th grade in elementary school and they have one high school (very big). Frisco is committed to being a 4-A school instead of 5-A so they will have more high schools than Plano to keep their high school's smaller.
To be honest, I think if you picked Plano, Frisco or Allen, your child(ren) would get a good education.
Good luck.