Ive come into a bit of an issue lately regarding shopping cart software, and i would like some recommendations.

I have been an OsCommerce developer for years now, and im finding alot of my clients are wanting updated looking backends ... OSC is fantastic, but the fact that its not being updated anymore and that its clunky and table based is taking up quite a bit of my time.

I have built a few sites on Magento, and although it gives quite a good backend, it is the slowest shopping cart i have ever come across in my time, that and the fact that modifying it takes years, has convinced me not to use that again.

So, i like any input as to what people are finding good in todays open source shopping cart software.