Actually, there never was a POD 2.0, the first 2.x series released to the public was the 2.1(although it said 2.0 on the casing).
Here are the main differences...
POD VERSION 2.1 IS DIFFERENT FROM 2.2
Latch mode was added
- Hold down Tap Tempo and Manual at the same time
-- Manual and tap tempo will flash
-- All dials act as if you are holding down Tap tempo
Delay carry-over was removed to allow for Latch mode
- When you switch patches your delay will not carry over, it turns off
POD VERSION 2.2 IS DIFFERENT FROM 2.3
Some amp models
were slightly changed
- Most noticeably the marshall sims
Some cab models were changed
- Most noticeably the NO CAB sim. Sounds a whole lot better.
**Flextone versions changes are the same as POD after 2.1. But, the Flextone skipped 2.3 and went to 2.4. 2.4 on Flextone is the same as 2.3 on POD.