I haven't read a single post about the phone freezing. If it's freezing, it's most likely an app.
I juggle three email accounts: Gmail, Exchange through Touchdown, and an Outlook.com account. I have no problem quickly receiving and responding to email. No freezing. I use and rely on the phone 100% for business. Mail management from the device is no problem.
You don't tell us how you are accessing email, such as through the default app, K9, or Touchdown. If you are trying to use Yahoo or Hotmail accounts through the default app, you may need to subscribe to those providers' premium services to properly manage those services. Try K9 and Touchdown.
I have also not experience any freezing and I peruse some other forums daily and have not seen a lot of it. I do know there was a problem with the Yahoo Finance app freezing, but it was updated. I noticed that after it would freeze the phone would close it and start working correctly again.
I use Aquamail and absolutely love it. I have 2 mail accounts right now. You can have many accounts if you pay for the premium app or 2 with the free one. Aquamail is infinitely customizable and works with many different email providers.