I would be afraid to use a pirated version of this. Certainly the authors are experts in cracking and countermeasures. They could do sneaky stuff like pretending to work and then breaking later, or silently produce wrong output.
I heard a rumor that the cracked version calls home with your identity and blacklists you for life. Don't think it is true though. (Edit: I think what they do is they embed your key into saved files, and if a key leaks, blacklist it such that later versions cannot open them.)
If a database was created using an instance of IDA that was running on a known blacklisted key you'll get a "Sorry, you can't open this database because it was created using a pirated version of IDA" message, and if you try to open a database that's missing the license info you'll get a "Database is corrupt." message. It's still pretty easy to patch out these messages and open the databases anyways though.
There's also a map [1] on the old IDA website showing geolocated IPs of users that tried to request updates using pirated keys.
I heard a rumor that the cracked version calls home with your identity and blacklists you for life. Don't think it is true though. (Edit: I think what they do is they embed your key into saved files, and if a key leaks, blacklist it such that later versions cannot open them.)