I found this forum via a google search for "Tom tom N70 problems" which, lead me to a great thread that showed lots of others who have problems with the N70 dropping the bluetooth connection to third part AND official tomtom GPS devices.

However, that thread hasnt' been updated for some months (over a year). So before I upgrade from my 6600 to a friends 12 month old N70, has the TomTom issue been solved?

I have tomtom mobile 5.00 and a third party GPS device. Both work perfectly on my 6600 with speed camera POI's from pocket GPS world.

Hi,
You probably found comments from me on one or more of those forums.
I'm running TT5.202 on an N70 with some success.
However it works only with certain limitations. Basically you can't use addon POIs such as Speed Cams etc. I use a BT 321 Holox GPS and run Traffic on a regular basis.
You can get around the limitations of the addon POI problem by changing the TomTom poi.dat file for one made up using a third party free software from DirkSoft (sorry haven't the link at the moment). With this programme you can make a new poi.dat file which contains the POIs you want. The limitations are that you have to use existing icons. I use a Panoramic View icon which is a picture of a 35mm Camera for my speed cams. It's a fiddle but it can be automated in a batch file so that with each camera file update you can quickly update the phone.
I have also updated my phone to the latest software V 5.0705.3.0.1

Edit.. Here's the link http://www.tomtomsatnav.info/poidat.html
It wasn't DirkSoft after all but Ray Flanagan's site. Apologies to both.

Hope this helps you make your decision.