I'm on my third. I ordered my first the day of the announcement. I have not seen any moisture issues with the display. I wear mine all day, minus charging. I work out 3-4 days a week, so mine is exposed to lots of sweat. I also wear mine while doing yard work, so it gets some dirt on top of the sweat. Has your Band taken any hard falls or shown any signs of cracks or openings around the display?
My issue is primarily corrosion of the sensor around the charging port. It gets to a point that it won't charge easily. With the last one, it also started to cause a rash on my wrist.
I've also had problems with the cover on the battery compartment wrinkling up. The cover started coming off with the last Band. I think that comes from my wrist bone pushing on the cover while I'm coding all day.
I'm getting about three months with each Band.
I haven't had any customer service issues. I ordered my Band from microsoftstore.com since I don't have anything close by. Each time, I request a call from support via the online support page. They've never hesitated to replace my Band. They did ask for pictures the first time. And they did remind me to wipe my Band off after getting wet or sweating. I was. The second time, they replaced with no questions or advice. I did an advanced exchange each time, so I had my replacement in two days without having to send mine in first. I've been impressed with the customer service every time. It is remarkable.
While it is annoying to have these issues with the Band durability, I cannot complain about the customer service at all. I'm hoping these durability issues are resolved with Band 2, if there is ever such a thing.
My goal was to get a year out of my Band. I felt like that was reasonable for an activity/fitness device given the potential punishment it would take while doing various activities. If Microsoft keeps up the great customer service and replacements through the first year, I'll be quite happy. I wouldn't hesitate to buy another after the year has elapsed.