DNN is great but ecommerce is one of its weaknesses. I have made a deep research for a client and the conclusion was to use Magento (It's best ecommerce OS I know about, and I checked several)

I found one thing in Magento that I did not like, the import/exprot feature which was very complicated for none expert. It was about 6 months ago and things may have changed though.

Although I have seen some reason modules for e-commerce with DNN I've always felt let down in the end.

Like others have said - if your main requirement is e-commerce, do consider other options first.

DNN has strengths outside of this, and with some development tools at hand I'll personally stick with DNN and build modules to compensate for where I feel let down by others.

Thoroughly look over any trial or demo versions and see that they will meet your needs.  Having been recently let down after discovering and reporting a bug in Catalook earlier in the year, it resulted in the feature effectively being worked out of the module... creating more work for me and a right nuisance.  I wouldn't have taken such a product had I known there was a bug and especially if I'd known it wouldn't be fixed.

That's not the first DNN e-commerce module that's let me down either. Be weary of features that aren't really there such as multi-currency. Make sure it's properly described or you can see it in action else before you know it the definition will not be what you're expecting.