Hi Mike,
I know there a people here better suited to answer this but I'll give it a go (some of what is my opinion).

If you look at the verision history you'll see what has been added, changed and fixed since 2.60. As far as I know there are no new actual commands however the new #CONFIG and the conditional compilations features are a HUGH benefit. Perhaps not the #CONFIG directive, it only makes what was previously possible a whole lot easier but the conditional compilation features are absolutely GREAT - much sought after.

Applying the upgrade should just be a matter of installing alongside with your current installation. You can switch back and forth between versions if you need. As far as I know that's the way it's always been and there's no change. If you install to the default folder you'll get PBP3 directory in which every thing is located - it should leave your current 2.6 installation alone.

Don't know of any example routines for using the MSSP-module in I2C-mode but it shouldn't be too hard after initial setup. There are examples available to use said peripheral in SPI-mode and I would guess using it in I2C would be quite similar. I have never used I2C though so I may be way off target on that one....

Hopefully those with deeper knowlege and understanding (read Darrel ;-) ) will chime in to elaborate and correct any mistakes I may have made.

/Henrik.