We've been using this for our Excel file processing for the past couple of years now. If we're not importing massive data sets from Excel files, we're exporting to custom specialised reports. The main factor for us is performance, especially since we work with large files and do a lot of processing in the files while generating... and XlsIO works faster than any of the other tools I've tested. I'm using a very popular grid control from another party and wrote an export to Excel extension function for the grid using XlsIO and it works at least 3 times faster than the grid's internal SaveExcel function. They're also up to date with the latest file formats as Excel versions get released and upgrades are available 4 times a year. Had a couple of small issues before, but the issues were fixed in a couple days and a patch was supplied to me.