I just got the Alexa HEOS skill up and running on my S730H and thought I'd give my general observations and suggestions (since some posters were wondering what is the benefit or use case, etc.)
I bought a Denon S730H after we moved to a new house late last year, I chose it because it was a good midlevel/basic receiver with Airplay, HEOS smartphone apps and streaming services, Alexa control, and multi zone. I have a 2 zone system set up, with Zone 1 being backyard speakers, and Zone 2 being my living room speakers. I set it up that way because Audyssey dramatically improved my backyard outdoor speakers (TIC GS3). Inside I have some classic DCM speakers that sound pretty good already on their own. The S730H drives the outdoor speakers louder than I will ever get to play them, unfortunately (neighbors!)
We have 1 Echo Dot, a couple of Dash Wands, and 2 Fire TV's that have their own Alexa remotes, all of which can obviously be used for Alexa commands. Now, Alexa doesn't do anything I can't already do with the Denon AVR and HEOS smartphone apps. But it does feel kind of magical to be able to say, "Alexa, play Jimi Hendrix on deck", "Alexa, volume 50 on deck," or "Alexa, turn off deck" and have everything up and running by itself (with the Dash and Fire TV remotes you don't say "Alexa", you just hold the button and issue the command.) Someone asked about how to switch inputs on a receiver, here is a list of available commands (including switching inputs):
The command list doesn't mention album names, but you can request specific albums (if you have a service that supports that.)
With the receiver interface itself, HEOS, and Alexa skill all more or less running on top of each other, there are bound to be some snafus. But after some setup hiccups, it all actually works very well. Here are some goods/bads I've encountered:
1. 'Room' and 'Zone' can mean different things at different times, even Denon uses the terms sometimes generally, and sometimes as a specific term referring to a hardware or software feature. For any set up that doesn't involve a receiver in multi-zone configuration, it doesn't really matter as the device name is typically the room it is located in. The Alexa HEOS skill only recognizes room names, not zones. So unfortunately I can't ask Alexa to play music in my zone 1 or zone 2. I can ask Alexa to start playback on the main zone, then make any zone changes in the HEOS app (first world problems!) AVR zone control would be a great new feature to add to the HEOS Alexa Skill.
2. The Alexa skill didn't work right unless I used one of the default choices for room name (by that I mean when you edit or pick a name for a room in the HEOS app.) All the default choices are room names which doesn't quite fit a multi zone receiver, so I originally custom entered 'Stereo' as my room name, and "Yard" and "LivingRoom" as my 2 zones. The Alexa commands didn't work very well with any of the custom room names I assigned to my receiver- that was very frustrating because it sometimes recognized the name and sometimes didn't. At some point I just picked "Deck" from the drop down list, refreshed my devices in Alexa, and then boom- everything started working perfectly.
3. The Dash Wands in particular are great for me, because they are cheap (first one was free after $20 Amazon credit, 2nd was $7 on sale at Amazon a couple of weeks ago) and just as importantly are weather-resistant/splashproof. This means I can keep 1 or 2 Dashes outside (we own a spa) as voice remotes (I should have bought 2 when they went on sale, but will pick up another later.) On a side note regarding privacy, I don't think the Dash wands are listening or recording anything unless you press the button (they run off 2 AA batteries and are basically sleeping until you press the button- that's why you can't use them for timers.) When the rainy season is over I'll maybe put an Echo Dot on our patio deck. Again, these controls can all be done on a smartphone (I really like the Denon/HEOS smartphone apps!), but this does add some convenience.
4. If you are using Airplay from a iOS device for playback, you can still perform some rudimentary Alexa commands even though the receiver is not playing through HEOS. You can skip, pause, and still of course control volume.
5. This is a limitation of the HEOS system, but I don't think you can ask Alexa to play some custom playlist you've made in your Amazon Music or other music service. IIRC, in the HEOS app when you choose one of the services, you mostly get universal choices for playlists and radio stations, artist search, but not user-created playlists (there are a lot of available choices however.) So if I made my own big party playlist, I would play it via Airplay from a phone or tablet and then have the basic Alexa controls I mentioned above. With Android I assume you could play through Bluetooth instead and have the same controls through Alexa (since Bluetooth supports those basic functionalities.) HEOS only is somewhat limiting, but HEOS + Airplay or HEOS + Bluetooth gives you a lot of options.
6. If you only have 1 HEOS speaker or 1 receiver that is only playing in 1 zone, the Alexa capability would seem to be much less significant. Especially if it's in your living room or home theater where all the remotes are right there on the coffee table anyway. But for multi zone and multiple devices this is pretty cool, especially if you have zones outside. The next portable speaker I buy will be a HEOS enabled one (maybe a HEOS 1 or 3 for the kitchen or our side patio), and will seamlessly fit in with minimum set up.
7. The Logitech Harmony hub system with matching Alexa skill offers a lot of additional capabilities. As long as there's no overlapping name assignments (which would probably confuse Alexa on whether to invoke the HEOS or Logitech skill) I could see it all working together seamlessly. These days I stream almost 100% of the time, so don't need a Harmony hub myself.
8. I was really late to the smart home thing, but I have found Alexa in general to work great. You don't need any additional hardware like a central hub, and there is a lot of inexpensive Alexa-compatible hardware. I own 3 or 4 TP-Link smart plugs, a Nest thermostat, and a Ring doorbell. I mainly just use the smart plugs, but nothing was expensive and I'll probably try using the free IFTTT service to create little services (turn on certain lights when the Ring detects motion, etc.) So getting an Alexa-enabled receiver was a pretty easy step for me.
6. I can't wait until summer!