What's new vs the original OP-1?

Hardware improvements:

• Velocity-sensitive keys (original had none)
• Tilt and accelerometer sensors
• 24+ hour battery (vs ~16 hours)
• Improved speaker
• USB-C (vs mini-USB)
• FM antenna (improved radio)

Audio quality:

• 32-bit float internal processing
• Improved DA converters
• Stereo recording on all tape tracks
• Higher sample rate option
• Better headphone amplifier

New features:

• 4 tape styles — Studio, Vintage, Porta, Disk
• Stereo engines — Many synths are now stereo
• Dimension synth — New ambient engine
• Improved radio — Better FM reception
• USB audio — Works as audio interface
• New sequencers — Hold and Motion
• Velocity — Keys respond to how hard you play

Same but improved:

• Same form factor and layout
• Compatible with many OG patches (with conversion)
• Similar workflow
• 4-track tape concept retained

What stayed the same:

• Button layout
• Screen and encoders
• Basic tape workflow
• Synth/drum/sampler modes

Is it worth upgrading?

• If you want stereo and velocity: yes
• If you're happy with OG OP-1: it still works great
• Field is premium tier — significant price increase
• New features are meaningful for certain workflows