If like me, your familiar with the old Caligari GUI then 7.6 and 7.61 will set you back a bit in terms of navigating the GUI in them both. The old GUI was pretty easy to use as all the button icons were clearly visible compared the the single row concept used by version 7.5 and above. Now you have left click hold to expand the menu bars to select tools. One bonus I do like in TS 7.5 and above is the Link Editor window which appears to be very useful for accessing RSOBJ scripts for things like import and export add-ons. I have several already installed in the LE.
I like the old style the best as you could leave the menu bars fully open to access the different icon buttonsquite instantly. Both 7.6 7.61 have some serious issues with the lack of many 3D model file importer and exporters like TS 6 and earlier supported, but you can use the Bridge feature in 7.6 for importing and exporting older models. Sadly, both 7.6 and 7.61 don't even include a COB or SCN importer making it somewhat limited for practical purposes. I still recommend installing 7.61 for it's active support of RSX plug-ins and add-ons. Sadly, 7.61 also lacks a built in scene renderer. I believe I saw an RSX plug-in for a D3D renderer somewhere on the web.