Old thread, but I just bought a 2015 Genesis 5.0 Ultimate, and I've had a few problems I've been wanting to catalog anyway.
1. It pulls to the right. This may be under-pressure in the right front tire; it usually matches the front left, but sometimes reads 1psi lower. This gets tiring on a long drive (I commute 2 hours each way a couple days a week).
2. Lane Keep Assist seems to be miscalibrated. It *could* have something to do with the above (pulling to the right), but it only seems to care that I'm nearing the lane marker about half the time (when it's locked onto the lane markers). It'll give me a lane departure warning, but will only attempt to correct about half the time.
2a. And every once in a while in a right turn, I'll drift too close to the outside line and it'll pull hard back into the curve (to the left). When the curve is finished, it continues pulling to the left until I exit the lane (unless I correct it myself).
3. My sunroof visor (the 6" piece of glass between the windshield and sunroof) shattered and the seal around the edge started coming off. I noticed it shattered when I heard glass bits tumbling across my roof and heard the seal thumping against the sunroof. (Other models have had recalls for this issue, citing a road hazard if the seal comes all the way off. I'm not sure why the Genesis hasn't.)
4. The A/C doesn't seem to regulate properly. I find it continually blowing cold air at me as I inch the temperature up (a degree or two at a time) to 80 or so. And sometimes it continues blowing warm air at me until I inch it down to 68 or so. I used to have a car I could set to 74 and leave it like that forever. In this car I'm constantly fiddling and it's never right.
5. There's a rubber gasket between the high center brake light and the back window. It dried up and cracked (due to sun exposure, I assume) and is now sort of dangling. I'm going to tack it up with some rubber cement, but that's sort of hoopty.
6. Twice while driving in the rain, my Blind Spot Detection on the driver side has lit up when there was clearly nobody in the lane next to me.
7. The gas fill-up door is absolutely chintzy. It's light plastic and not rigid enough that the latch lines up when you shut it, and I find myself fidgeting (carefully) to get it to shut correctly. My 2006 Sonata gas door was more solid than this one, and this is a "luxury car". :-\
8. I haven't verified this yet, but my wife says the passenger seat heats her back but not her <ahem> seat.
Not strictly car issues, but tangential gripes:
9. I thought this was a much worse problem until I figured it out. I thought the Heads-Up Display was spontaneously shutting off mid-drive. Turns out it just wasn't visible when I put on my polarized sunglasses.

10. The mobile app is about the crappiest mobile app I've ever used. (Nothing about it strikes me as intuitive.) Half the time it times out while trying to get an update, and one time it insisted my car, which I was staring at, was about 25 miles away, even after a "successful" location update.
11. The obvious omission of Android Play with the 9.2" DIS, and the ... meh ... navigation software built into the unit. I find myself mounting my phone right next to that big 'ol display and using Waze instead. It's almost like putting the new smaller TV on top of the older cabinet TV. (Rednecks will get this.)
These are all relatively minor gripes. I'd like to get the first few addressed, but they're probably calibration issues of some sort.