I just set up mine with HS3 for RPi.
I don't know how different they are.
You can edit the names of the devices in HomeSeer in the "Voice Command" box to give them easier to use voice names.
e.g. "Downstairs" instead of "Downstairs Thermostat Root Device".
You need a My HomeSeer account, Free through their website, links in to your HomeSeer.
Go into the Alexa app, search for HomeSeer and enable the skill. There are two, one uses the internal Echo API, the other uses the pass through method.
You can use both together, so no harm in enabling both.
A popup will come up asking for the My HomeSeer login, and then link the accounts.
Then simply tell her, "Alexa, discover my devices." And she'll import all of the listed devices in HomeSeer.
The Alexa app will show the list of devices in the Smart Home area.
If you want to rename a device, delete it from the Alexa list. Rename it and rediscover devices and she'll update.
If you don't delete it first she will have both the old name and new name listed, with the old one showing "offline" since it doesn't exist anymore.
You have to delete devices through the webpage interface through the Amazon page. You can't do it in the app.
The verbiage for the API is more natural.
e.g., "Alexa, turn on the Living Room Light".
The other skill can do more, but the verbiage is a bit more convoluted.
e.g., "Alexa, tell HomeSeer to turn on the Living Room Light.
Her responses are different too. With the API she simply answers "OK".
IIRC, the other skill replies, "OK, I will turn on the Living Room Light." Or something similarly verbose.
So far I've been able to do everything I wanted to just using the API.
I can control all of my OmniPro UPB and Zigbee lights (and soon ZWave), my thermostats, flags, outputs and virtual devices in HomeSeer I use for things like turning on the TV or changing channels (through the DirecTV plugin).
Quite a full suite of options so far.
I can't do UPB scenes through the Omni plugin. I need to use the SpudUPB plugin. For that I need another PIM.