In the case of the Monteverde stub nib, it has a fairly small sweet spot. It's nothing that I classify as a deal-breaker, but it is something that causes me some frustration. Like all pens, it has a personality when it comes to writing, and I've come to learn how it likes to be treated when writing. When held properly, it really is a beautiful, well-behaved nib.
That being said, specialized nibs create specialized opinions. What I dislike about a nib, another person might love. So, take my quibble with a grain of salt.
Overall
As a pen, the Invincia is beautiful, eye-catching, well-balanced, and fun to use. I love the amount of variation I can get from the steel stub nib, and I love the weight and feel of the pen in my hand when writing. Apart from my own nib preferences, this pen has no downsides for me. I'm happy that it's part of my collection alongside my Artista.
You can find the Invincia in a variety of colors and nib types from Goulet Pens. As I'm writing this, they have black, blue, lime green, and orange in stock, all of which look as nice as this one.
(Goulet Pens provided this product at no charge to The Pen Addict for review purposes.)