This is a safe space.....
Confess to the mistakes you have made in order to help others avoid doing the same.... With a healthy dose of self deprecation.... 
For me the most common is not researching a purchase of new tech. That said, that mistake lead me to invest in a raspberry pi for the first time. 3 more pi's later.... thankfully I don't need to justify my addiction....
Similar. I asked for a Zooz Zen25 for Christmas. The return process was a lot more complicated and awkward because my mother-in-law bought it for me.
I bought into Wink... Nuff' said...
I forgot to add a caveat around paying out to other platforms, my bad....
Oofph where to start. When I started I wanted color smart bulbs everywhere. Wish I knew how annoying bulbs connected to switches are.
The latest were some glass break sensors that I have no idea why I bought them, as echo speakers actually do a great job at that.
Ikea and Linkind are 2 companies I love to hate. I've got a ton of buttons from each, at least the Linkind came packaged with an excellent plug for 15 bucks, so can't get too upset there. Ikea on the other hand, I can't stand how many of those buttons don't work, even the button that came with my shade that works perfectly, doesn't work.
Echo speakers... what can I say, I work some midnights and have free time and woot always has sales, lol. I've outfitted 2 other houses with my leftover speakers after I learned whole home audio with 15 echo's just doesn't work, and their is no reason to have one every 10 feet.
Lastly in-wall switches. I bought a bunch of centralites from ebay for cheap to find out they were the companion switch to 3 way switches.
#1 hint I can give is that echo speakers rock, Echo shows suck more than anything has ever sucked in this whole sucky world. Along with that fire tablets make great dashboards, just DO NOT connect them to the internet and update before you know how to root the things to get rid of the Amazon garbage.
Thats about all I can think of right now, though their have been plenty of other incompatibilities, some have been worked out, ie. switchbot bot, those wonderful Tuya 4 gang switches and their 4 button remote, those are real gems for Hubitat.
That's my happy mistake... The IKEA on/off buttons I now have connected to a Conbee2 stick on a rpi, connected to HE via the deConz Community integration:
I also used this to join my Hue dimmers for a period, until I started using the latest Advanced Hue integration that includes push notifications from the Hue bridge, including these accessories.
I thought about that but I really dont want to play with Home Assistant again. Too much work.
It's not through Home Assistant, "simply" by installing deConz and the associated web-based config app, can't remember the name right now. This exposes an API that the drivers make use of to receive notifications that the button has been pressed.
I'm not going to claim the setup is rock solid, thinking more of the blame can be laid on my setup of the mesh, rather than the drivers.
Not really a regret. I was using chromecast based speakers everywhere simply for the multiroom music (I don't really use voice control). Then the sonos lawsuit happened and I lost a lot of functionality. Replaced with echo's...
Uff this. Having said that, without Wink I don't know if I would have ever fully bought into Home Automation and gone the HE route.
It got me addicted, wanting more AND realizing how important local is.
Oooooo, sounds like a new project for me.
Tah-dah! Thank you, thank you, I'm here through Thursday... 
@erktrek - we may have a need for your professional services.... If anyone takes the last post seriously...
A perfectly professional response....
Buying several zigbee outlets to improve my mesh, and then let them sit in the boxes for several months because, honestly, I just don't understand the zigbee mesh that well...
I went zwave at first.
I have a lot of Arduino, LoRa home brew devices connected to hubs. Mistake was building/Soldering/Coding my own controllers down to the component level to control Critical devices that need to be up 100%; Pumps, Solar chargers, etc.. Even built my own DC to DC buck converters. Many Many hours, years, of constant tweeking and refining. Always needing to fiddle with them. DONE!, going with off the shelf stuff where possible. Homebrew stuff now limited to non-critical sensors like temp, voltage measurement, etc.. Learned a lot though, but way to much TIME and money invested, mostly time.
Buying too many HUE bulbs when they were on sale. I now have enough version 1 bulbs to light up 5 blocks. Don't buy more than needed or you will ended up like me.
I wouldn't say I have bought too many, or at least I haven't got many in reserve. But I was thinking the other day that while the long ~20K hour life-span of the bulbs may feel like a good selling point at the time, the rate of change in technology is much faster. So it will be interesting to see what I do in another 2-3 years, whether I need / want to move on to something else, even though my bulbs may still be working perfectly.
Download the Hubitat app
