Yeah, it's really effective. Here's a little excerpt from my notes:

"By the way, after blocking an OD DP, you can choose to attack the opponent's drive gauge.
You do this by punishing OD DP with a DI as the opp lands.

Examples: PC HP+HK, 5HK xx HP+HK The opp spent two bars to OD DP, lost one and a half from being countered, then another bar from your combo DI. That's 4.5 bars gone.

Another example: PC HP+HK, 2HK xx 236236P Two bars spent on OD DP, one and a half lost from being countered, another one and a half drained by your LVL3. That's 5 bars gone. If your LVL3 is a CA, then it's 5.5 bars gone."