Anyone got any experience of Magento?

Yeah, its pretty darn simple. Made a site for a client in under a day. It was sorting out all products that was tough. How many items are going on there?
I've only ended up at magento's door because there's a particular plugin that a client wants to use that's Magento only. I've installed it locally using MAMP this aft and that was a right ball ache!... but it's now running so I just need to get to grips with the UI now!!...
I've done some playing and some reading (mainly on the admin interface) and it feels like I'm getting somewhere with it. Not sure I would like to tackle developing a custom theme but bastardising a free one seems quite simple. #famouslastwords
What's your experience with web development at the moment, say in wordpress or another CMS. It will take a significant amount of skill to develop it from scratch, but you could learn to manage from the back end pretty well when the site has been developed.
I can build static sites and am learning modx. Can modify Wordpress themes but have never had the time or inclination to try developing a site from scratch for WP.