The ability to create an easy-to use product from scratch, it's also great that you can easily change features with your customers without hassle or delays! A bit pricey compared some other options out there too - but I understand why they were charging more for their platform/solution (which was excellent).
Nothing really negative at this time of writing in terms my experience so far as we've not had any issues since going live 2 months ago now either which has been fantastic :) Great support team who have dealt quickly & effectively w our requests over email when needed plus always happy chatty via IM during business hours if required even though sometimes hard given distance differences between UK / US offices etc.. Overall satisfied customer base thus no real complaints yet apart perhaps just wish pricing could be lower? We are solving two big problems by providing one system where clients don't need multiple sites setup separately each creating separate admin.