As the first card spoiled from its set, Burner came out of the gates swinging. This is a very strong card, giving Shapers HQ pressure they didn't previously have in-faction. It's kind of like a pseudo-Legwork, in that you see three cards from hand. That alone is useful, in that you gain a fair amount of knowledge about what gameplan the Corp is on, and what they're currently prepared to do. But you also have the ability to disrupt those plans and set up steals for yourself.
Here are a couple of modes this card can function in:
See combo threats, scoring tools, or econ bombs in hand, and sequester them safely on the bottom of R&D for free, where they can't even be immediately recurred.
See agendas in hand, and clear out the chaff so that your run back on HQ next click is hitting a target-rich environment.
See agendas in hand, and put them on top of R&D so that your run back on R&D next click is guaranteed* to hit.
You can also combine these effects, ie by bottoming a dangerous threat while putting an agenda on top of R&D. Note that the last one can be disrupted by the Corp drawing or shuffling before you get access, so be careful about deploying this tactic when a Spin Doctor is on the board, or when playing against Ob with a shuffle trigger in play. A Corp player with a scored Basalt Spire can also pull the top card off the deck and into hand by spending a counter, so be careful.
All in all, a great card, and one of the reasons Shapers are ascendant with the release of Rebellion Without Rehearsal.