My ascensions: 1. Lawful dwarven valkyrie 2. Chaotic elven wizard
I feel like I've been killed in cockatrice-related incidents at least ten times.
Made it 98% of the way through once as a Ranger before dying to Jubilex's illness (after I had summoned him peacefully, and wanted to get him out of the way on my stash level before ascending... eughh). They really should give you more indicators of how close you are to death-by-illness in the status line, like with sliming.