We currently use Linnworks to manage our eBay, Amazon, Play and Magento store (www.dinkycartridges.co.uk/). We find that it works very well for eBay and the Linnlive listing tool saves loads of time. Amazon integration often seem to miss some products when updating inventory and can cause us to oversell. Playtrade intergration is ok but for some reason it doesn't download all of the orders, but i not sure if this is a problem with play rather than Linnworks.
The Magento integration work without any problems and link with out inventory of cheap ink cartridges listed on the site.
Overall i would recommend Linnworks, when you compare the product to the price eSellerPro charge its good value.