I've been running TomTom5 on my 6680 for about a year now, and although TT is now out ( for Series 60 ver 3 phones ), the 6680 is still running very effectively.
Just bought a series of cd's with the maps of Western Europe, and have successfully downloaded the entire map of France onto my MMC ( had to upgrade the MMC, as it was only 512mb before, now running 1gb )
In the end , it was quite a smooth process, and seems to be working quite well. Very pleased in the end - I bought the original TT5 software from eBay for �3.00 !