Thing is, I'd be happy with stock GP edition, didn't seem to work 100% though. I know it's only a small thing but the transparent toolbar went solid when you were in any apps, isn't it supposed to remain transparent? At least in apps like Google Maps where there's full screen content?
Nope, not even on the Nexus 5. I've had no problems at all with the Google Play edition conversion on my HTC One. It is designed specifically for that phone, after all, so it should work 100%. That is as compared to something like CyanogenMod that's a third party thing.
There are two types of ROMs out there. There are ROMs based off stock HTC software, and there are ROMs based off AOSP code adapted for the device. In the case of the HTC One, it has a fairly AOSP ROM in the Google Play edition, so you could say there are GPe based ROMs as well.
If you want/need Beats and the HTC camera, you must be on an HTC based ROM. The code for these features is in the HTC code, so going with CM or GPe will lose those features. It's not just something that people have forgotten to add. There are alternatives though for AOSP based ROMs like various sound mods available on XDA and camera apps like Focal that add more features over AOSP if you go that route.
The HTC One confuses things a little bit more in the fact that the GPe ROMs actually still uses HTCs kernel and have some of the underlying Sense code in the kernel. This allows them to use some features like the IR sensor and if I recall correctly it enabled better USB OTG for me, but I can't remember the details there. So GPe ROMs give you the feel of AOSP, but better support for the device than ROMs like CM.
For me, nothing compares to GPe. On my N5 I'm running CM now because it is true AOSP and therefore nothing is really missing from CM. For the HTC One I run GPe because it's the best of both worlds and gets updates quickly. In fact, I just pulled mine out this morning and it's bugging me to update to 4.4.2.