Saw non-compliant DCC today as Isaac's Hostel in Dublin. Not too bad as the choice was in the cardholder's hands (and expecting worse I'd already asked for Euro when inserting my card). Instead of asking me to choose an amount it said:

Amount
US Dollar $24.xx (I forgot the exact amount)
No / Yes

Thus it didn't present a choice of currency it instead asked if the amount was okay. Which doesn't imply a choice. Hitting no put it through in euro with a DCC-free signature slip and final slip.

Not too awful but easy to slip up since it isn't an active choice.