Some I've run into are:
- There is a button battery in the shifter. So you have to carry extra button battery.
- I've run out of charge on the rechargeable battery more than once but that's because I'm lazy and I like to take unnecessary chances. Usually I can go for a while w/o recharging (I dunno maybe like a month depending on how much I'm using the bike).
- I've had to "bleed" mine a few time because it develops (up/down) play. SRAM has a tool that comes with the post and a simple procedure to remedy this. It takes like 2 minutes. I think basically you let some air out or something like that. I kinda take this as a positive because other cable droppers I've had they all developed this up/down play eventually and there was no way to fix it or it's difficult.
- This one time my batteries drained prematurely. They died after like 3 rides and I was stuck in the middle of the Virginia Southern Traverse with no shifting and no dropper. My theory is that the shifter and seatpost/deraileur stayed connected together after one of my rides and drained the batteries. It's supposed to disconnect and connect automatically. But it is also possible that I just forgot and they weren't really charged at all. As I am an old man now, my memory is not so good. I will probably get some extra batteries at some point and carry them with me when I'm doing day long rides or longer.
I think the best thing I like about it is that the feel of it never ever changes (other than the bleed thing). With cable actuated ones, I felt that over time things start to feel slightly different (not in a good way). I also like the fact that it doesn't take too much thumb muscle to activate it. It can be an issue when you are out there riding for 12hrs. That's why I used grip shifter for ages.
That said I don't think it's worth it to spend $800 for a post when other much cheaper options exist. But I can say the same about lots of other bike parts. If you can have the best of the best, why not?