No, the code isn't bad at all. It's actually a very good example of what is possible with SilverStripe.
There is a good deal of missing functionality IMHO though, particularly when it comes to order management and product management. If your primary requirement is an online shop, as opposed to a flexible CMS with integrated modules, then there are better options available. I think SilverStripe recognise this, hence the direction away from the (current) ecommerce module.
So, the option is to patch up the current ecommerce module to work with SS2.4.0 or build some basic catalogue & order management and using the Payment module. This is where the willing participants come in, it's easy enough to patch something up with a bit of help from time-to-time but it takes a coordinated and commited effort to build something new.
I'm more than happy to look at what Jeremy has done and to help test and patch it if necessary, as for extending it - I'm leaning towards the "Payables" example when I don't need a cart/order-management and using an alternative for a more complete ecommerce solution ... unless we have enough willing participants ;)
P.S. I really would prefer it if we could get the willing participants!