I have been using Mage-World for many of my magento needs. I am currently using these extensions on my sites - reward points, one step checkout, IP checker, help desk, and more. These extensions are a fundamental side of my online stores, and Mage-World has been a great partner to work with.
Their extensions are well built and function impeccably, and their service is second to non as they are super quick to reply to support tickets and they were always there whenever I needed any help/fixes.
I highly recommend Mage-World extensions and working with Mage-World in general - they are a great Magento partner.