Well, if you have a device that's rooted, or are interested in rooting, the devs over at Dirty Unicorns have you covered. They host a whole bevy of devices.
Here is a list of currently supported devices.
While you may see them on XDA from time to time, they prefer doing their troubleshooting and general conversations on their G+ community.
I have run DU on devices for years. Back before DU I ran AOKP. They have always made a very stable and solid ROM. However, since their dev team has grown, so has the robustness (is that a word?) of the ROM. Both in stability and features.
DU v10.0 is no exception. This is arguably the best ROM they have released (at least in my opinion).
Great new features have been added like Smart Bar, Fling, and Pulse. See videos below to see them in action!
As many of you know, I have the Nexus 6P. I did not root my phone until just about a month ago, when I knew DU was getting close to an official release. I thought my Nexus was fast BEFORE I flashed DU. Man, was I wrong. This thing blazes now. I am enjoying all day battery life, even with moderate usage. I LOVE pulse. Pulse is a very nice yet subtle touch that just makes the overall experience so much better. The ability to theme is also an added bonus.
Speaking of theming, DU introduced "DU Certified". An app that shows you themes that are guaranteed to work with the ROM. Some of these themes are free, some are a couple of bucks, but it's totally worth every penny to be able customize your DU experience.
You can even mix and match theme attributes with the theme engine to let you find the perfect balance between 2 or more of your favorite themes.
Under Settings you have "Dirty Tweaks" which gives you access to even more settings that would not be otherwise accessible to you on a Google build. Things like rearranging your navigation bar, changing what displays in the status bar, LCD Density, Multi-window, App Circle bar, and system animations, just to name a few. (see any "N" build features in there?)
All of these items congeal to make one of the most solid and readily supported,recognized, and trusted ROMs in the Android community.
So maybe you are one of the unlucky ones to have a device that is not officially supported by DU. No problem. DU is only possible because of Open Source. Therefore it's only fitting that they are also open source. Get in touch with one of your favorite devs, or learn to compile your own build of DU!
The official Tutorial is here. Keep in mind, that thread is for Lollipop. However, keep an eye on the Official DU Twitter here and you'll be on the cutting edge of DU News.
Whatever ROM you are currently running, I can almost guarantee that if you switch to DU, you will not look back.
The level of support and a dedicated community should be enough on it's own to sway you in the right direction. Just familiarize yourself with logcat. Because in the unlikely event that you experience an issue, the devs will ask for (insist) on a logcat before they even look at the issue. This is not because they are being mean. It's because these guys do this for free, in their free time, and they deserve better than to have to spend hours looking for a needle in a haystack when you could take 1 minute to upload a logcat for them.
The community is all business either. They have a great sense of humor and an off topic section built specifically to pick on your favorite dev. (or just to talk about normal, non-DU stuff). They actively share awesome wallpapers and icon packs, and are always adding updates. If you are the early adopter type, you can even see posts for weeklies, and unofficial builds.
Get your butt over to the community and GET DIRTY!
Here is my current set up.
Here are some handy links for you!
DU Google+ Community
DU Official Website
DU Official Twitter
Get the full potential from your device, and give DU a chance!
Lest I forget. It goes with saying that DU is: