IE11 has the capability of running in Enterprise mode. We have Lawson go down to a lower level. The only issue I have run into has to do with LBI which you are not using.
We are on the latest ESP and MSP. We do an ESP/MSP once a year except for this year as we are going to Infor 10.
In version 10, there are still issues with the Object Viewer and the API Builder. You can at least change it to be compatible with IE8 by hitting F12. Design Studio in 10 still only works with IE.
We've had numerous discussions with the Lawson development team and despite the pressure we applied, there are absolutely no plans to support IE11 in design studio for the 9.0.1 version line. I've pointed out the logical inconsistency of the product supporting IE11 but the development tools do not, all to no avail. Consequently, the only work arounds are either to create a virtual machine on your pc where you can install IE10 or below (you cannot have more than one IE version on your PC at a time) or have a second PC. I've confirmed with Lawson development that none of the compatibility modes of IE11 will work either.