I really like Criminal's viruses. They're all such entertaining ways to get money. (Ok, Cache is kind of boring. But Pheromones is wonderful, and Gorman Drip v1 is hilarious.)
Anyway, Tapwrm is a worth entry into their ranks. The cost is cheap, and the install criteria is pretty minimal. (You can even install it off of archives!) It has some nice bounce-back effects - if the corp is super rich, this thing will pay serious dividends. It has counterplay, since it's a virus. And it rides that wonderful line where the corp has to continuously ask themselves "Should I purge? Is it really worth skipping a whole turn to stop them from getting 2? Maybe I should do it later?"
This card isn't powerful to be the focus of any decks by itself. But it's pretty good drip economy, that scales when you're behind, and it's cheap. I expect we'll see this start to show up in criminal decks - runner drip economy tends to be expensive, so anything with the potential to pay for itself on the first turn is noteworthy.