First of all, this is one of the most beautiful cards in all of Netrunner. Second of all, this ICE is pretty good, but is competing with other HB code gates
Brutal utility subroutines: Click Account Siphon is very powerful for the corp, especially in the crucial early game. A full fire means the corp can FA a 4/2 on their turn- choice targets could be a Vitruvius with a counter, or a Corporate Sales Team.
Value, even at last click- Enigma and Hourglass suffer from ignorability if the runner is on their last click-even if the runner has none to lose Nightdancer will still give you clicks
Taxing- 4 to break with Gordian Blade, Abagnale, Inversificator, and GS Striker M1 is respectable
High impact subroutines make Nightdancer a good target for a Batty game, as well as a good choice for Seidr Laboratories: Destiny Defined decks
Rare non-bioroid HB ICE, will surprise runners who think they are safe running at 4 clicks
Impact comes at a high cost- 6 is pricy for a 4 strength ICE
Weak to Cyber-Cypher and Black Orchestra (more evidence Black Orchestra is a mistake!)
Overall Nightdancer is an interesting alternative to the popular Fairchild suite!