I have the first generation of SNC and yes, there was a learning curve but I understand the new units offer some nice features as others mentioned above.
Check the Brother website or Amazon for the current cost for replacement blades and mats.
Accessories: other than weeding tools and perhaps some Frog tape (to hold down fabric/vinyl corners to the mats) not much more is needed.
Brother offers a site called Canvas that you can import/export designs, edit designs & layout, and convert to the fcm extension for the SNC. There are many designers who have their own sites who offer design files.
I have been very pleased with my machine however, I cannot offer any experience regarding other machines.