We install magento as standard for any client looking for an ecommerce store but you need to consider a number of things before deciding magento is for you.
Magento is infinetly expandable through plugins and will continue to grow for this reason alone, there is also an adundance of very good themes available so if your planning to grow as a business then Magento is a great choice for setting the early groundwork and will scale very well as products and customers increase.
Magento is pretty power hungry so your going to have to pay more for hosting, running it on 5 dollar p/mth host just wont cut it, some hosts also dont allow magento on their shared clusters at all.
There as some great plugins available for Magento and Quickbooks, not to mention Sage and XERO.
Magento is very advanced so will take a little longer to learn, the code is more complex so doing changes on your own may not be ideal is your experince is low and hosting will cost more so you need to take this into account when choosing your product.
I dont think anything can match Magento for scalability and feature potential but there are many other good shopping carts on the market, it really just depends on what you need from them for your business.