Quite a number of customers have used the ExcelLink successfully. Note that ExcelLink operation is pretty complex. It has to interact between the MS Excel spreadsheet via DDE and the TLServer program via TCP/IP, while the TLServer interacts with the PLC. As such, both MS Excel and TLServer must already be running before you run ExcelLink.
ExcelLink also need to interact with JRE, DDE and a lot of operating system related factors that can sometime affect the operation of ExcelLink on certain computers. If you encounter a lot of exception errors, try to run your PC "lean" with just the essential programs. When you load and unload lots of other program, the Windows O/S tend to become unstable and can affect proper operation of the ExcelLink program.
You can try to install the ExcelLink program on another PC and see if it improves the operation. In all the computers we tested we could leave ExcelLink running for days without even any communication error.