The ventilation system was very bad, since we smelled all sorts of smells wafting into the intake, including diesel exhaust, smoke, and even lighter fluid for a BBQ. When the front desk didn't do anything about the lighter fluid smell, a whole bunch of us had to storm the desk to get attention... I never heard of something so dangerous. Their sound system in the lounge also did not work for half of the cruise, but at least that didn't deprive us of sleep!
The ship docked a mile away from where they told us it would be in Amsterdam, forcing my 82 year old parents to walk that far with all their luggage.
I highly recommend avoiding the Helvetia and its sister ship Sun until Viking fixes these mechanical problems.