I definitely wouldn't call it plug'n'play yet. Alister's patches to the ST Ethernet HAL makes the integration easier, and they had a great integration document somewhere in the ST forums detailing what changes might be considered when integrating his patches. ST has also recently updated the HAL to improve the situation, but we're still running a hybrid of our own, Alister's, and STs patches.The biggest problems we've encountered are PBUF management (ST HAL assumes that the DMA descriptors are handled packet at a time which usually isn't the case; Alister's patches really helped here) and encountering operation serialization errors that kill the whole HAL such as attempting to do a MDIO transfer while the MAC is busy (which happens because we have a MAC management thread, lwIPs own TCP/IP thread, and then any ethernet interacting threads in the application -- locks are your friend and you'll need more than you think.)