Sprint and T-Mobile have started rolling out Android 2.3.4 update for Evo 3D and Sensation 4G smartphones respectively. Update will be available over-the-air on your phone, or you manually check by going to Menu > Settings > About Phone> HTC software updates > Check.

Update Changelogs:

Sensation 4G:

• Software stability
• Improvements in battery life, Trace dictionary, screen responsiveness, video playbook
• Improvements regarding device reboots
• Improvements to icon pixilation, Wi-Fi connection and screen/photo resolution

Evo 3D:

• Making additional preloaded apps un-installable by user.
• Updates to applications: Spiderman, Watch, Qik
• Device Lockscreen stuck in “half-state”
• Ability to transfer all contacts over Bluetooth
• Birthday one day off between contacts and Facebook when synced
• Random GPS coordinates issue – stuck in Taiwan
• Lockscreen displays 3-digit temperature correctly

You can read more about Evo 3D update here, and Sensation 4G update here.