Interesting! I had an almost opposite experience with the soup, after having tried it several times now.
For me, the soup has pretty horrible consistency (especially the chunks of tomato are both distracting and not tasty at all), and a yucky salty aftertaste. And I'm normally a big fan of tomato soup.
I originally bought it partially to experiment with using it as pasta sauce by adding a thickening agent to it - but after trying it the flavor is so disagreeable to me that I decided to forego that experiment entirely, as I don't think it would taste very good at all.
As for mixing: simply stiring will not do the trick for sure. Pre-mixing in my shaker before heating works well, as does mixing hot water + the powder inside a sealable silicon bag (just be careful of air pressure in the beginning!). By simply stirring it was impossible to get the lumps out (no matter how slowly I did it) and I ended up spilling a lot of it in the process as well.