I have the HTC One for Windows from TMo.
I did some further research and found that MS removed the pretty good turn-by-turn voice navigation for Bing Maps that was in WP7.x when they came out with WP8. IMHO it is an epic fail. The only thing they needed to do was replace the generic computer voice with Cortana and her A.I. and make the turn-by turn voice directions automatic instead of making you tap the screen. This also means that this thread belongs in WP8.1 forum not the HTC One (M8) for Windows forum. Sorry.
I installed Here Drive+ and spent the day using it. It definitely does not work with Cortana. Cortana will open Here Drive+ if you ask her specifically but that's about it. Here uses some generic computer generated voice. It sound like the voice from WP phone 7.x. Other than that it's not bad and displays some useful info at the bottom of screen that Bing Maps doesn't but I prefer the look and feel of Bing Maps and would MUCH rather have Cortana doing the turn-by-turn navigation. The only voice I hear coming from my phone should be Cortana otherwise the phone experience feels schizophrenic. (And that goes for other apps besides maps as well)
For example:
Someone text you an address. WP is smart enough to highlight the address and make it clickable but clicking on it opens Bing Maps not your 3rd party map app. Same behavior if you click an address in your contacts or an email or even if you ask Cortana for directions. Always opens Bing Maps then makes you click directions, then maps the route in Bing Maps, and then, finally, has a button to start voice navigation. That button will open your 3rd part maps. Cludgy, cludgy, cludgy.