OK, I'll part answer it.
Some kayaks have a rudder standard (or option to add one), some don't. I'm assuming the Nemo hasn't got the option to add.
Some kayak hull designs are such that they track straight fairly well without a rudder, some designs not so well....some so bad they're 'pigs' to hold straight. Either way you are always having to apply corrective strokes, or edge or lean the yak to achieve a desired course or turn. IMO there is one plus only for rudderless kayaks, and that is that they are simpler, having nothing to 'break'. Oh, also, they're often a lot cheaper, but at what cost long term? The downside is the continuous effort to hold a course, and the more advanced level of paddle techniques required to control the yak.
When conditions are tough, and we all know it can chage from idyllic to rotten quickly, a rudder is a great help. It can allow you to concentrate solely on kayak stability strokes (bracing) and forward propulsion strokes and technique, without the worry of all the steering correction strokes. This is especially important on long paddles as it frees you up to just paddle, drift, look at the scenery, and/or fish. The foot steering (hand in a Hobie) becomes second nature in no time.
So I hope you get my drift.
Personally I wouldn't enjoy yaking as much without a rudder, despite having an exceptionally high skill level.