The Palm GPS Navigator 3 package(Tomtom 6.030, Bluetooth GPS receiver, car mount kit, and car power adapter that powers both GPS and Palm Treo) is a decent package(got it over the holidays). The GPS is a SiRF Star 3 based GPS, and even though it does not come with an external antenna, it has decent reception in outdoor areas, though underground areas get poor reception. There is a connector for an external antenna on the GPS, but there is no documentation on what type is would accept, and Palm support has no information either.
Of course, since the GPS comes bundled with the Tomtom 6.030 software, it is fully supported, but I have run into the occasional glitch where the software doesn't talk to the GPS, and a soft-reset is needed to allow the software to talk to the GPS unit. That could be caused by my Treo 680, or something else, but it's fairly minor(I am sure there are times you just need to reset your Treo, just because an app misbehaves).
ler329: In the Tomtom software, do you have a problem establishing a connection to the GPS, or do you have a problem waiting for the GPS to get a "valid" signal? In the version 6 software, if you click on the 5 bars(lower right corner), you should get your route summary screen. On the right side of that screen you should see a summary of what the GPS itself has found, how many sats, your location, etc. If you tap on that summary, you should see the full GPS status, the circle showing which sats are around, and the signal strength to them(which will fluctuate every few seconds). This will show if the problem is your GPS reception to the sats.
dasbcjoker: what version of the application are you running? 6.030 is the latest app for the Palm. Check in Tomtom Home 1.5 and see which version you have, "check for updates" when you have your SD card plugged into your computer.