I've been using WebERP for around 7 months already. So far, the results are good. It is already fully functional and is the main software that I use in monitoring the finances of the law firm.
Currently, we are in the deployment of WebERP in a merchandising environment. Manual migration of subsidiary ledger data may be a chore specially for big companies with lots of receivables and payables, but the benefits could very well offset your efforts. Anyway, if you want to use the software at the start or onset of your business, it wouldn't be a problem because there would me no migration issues in having a clean start.
I am not well-versed in IT and programming but I learned about data importation and exportation through trial and error at the phpMyAdmin window. This is useful especially if you have a long list of customers and suppliers that you need to encode into the system.
Let me take this opportunity to invite you on December 13, 2008 @ the Dabawegnu Lab to know more about webERP and other Free and Open Source Software for Small and Medium Enterprises.