Magento has more features then any other open source platform as far as I know. All those things you need with a large online shop such as localised taxes, exchange rates, configurable products etc etc. For the right project Magento is great. Templating, theming and development is easy and extremely flexible once you understand it.
Magento excels at what it does but it is extremely overkill and time consuming for small sites with minimal products and variations. I think this is where Magento gets its bad reputation from. Magento will save you a ton of hours and headaches on large complex shops.
I agree on Gibbs. I have build a couple of Magento sites, but there are some things about Magento which can be improved if you ask me.
There is no product image management, there is for the product content fields/description but not for the product images straingly. Not for small webshops, Custom fields are quite hard to implement because of it's a pritty complex system. It's a bit slow, needs a quick server with lots MEM etc. I don't like the product CSV export / import. Styling is time comsuming. Further more its the best (opensource) out there I know of.
The best is picking a theme you like, buy this and restyle it. Styling takes a lot of time, but there is allot ready to go.
[ed. note: fourroses666 last edited this post 13 years, 2 months ago.]
Evolution user, I like the back-end speed and simplicity

Magento is also a good e-commerce plateform.