I got that unstable thing yesterday at the gym but the signal was strong and everything was fine so I just ignored it.
THE BEAST,,NOTE 3. SIZE IS EVERYTHING!!!
Wifi is very poor on my Note 3. We are migrating from a 4 iPhone family to all Samsung but still have 2 iPhones to go. Both iPhones work without issue even outside the house. The Notes lose connection continually, disconnect, reconnect, do not connect and message says not in range and message saying unstable or something of that nature. Definitely a deal breaker and the phones must go back before 30 days. Not getting stuck with a possible hardware problem. Looks like iPhone 5 for now.
When you first switched the phone on did it do a software update? If it did don't forget to do a factory reset.
As much as I hate to admit it there does appear to be some things Samsung need to address with the Note 3 but no deal breakers.
from my Note 3
If the apparent wi-fi issues are not fixed, it will be a deal-breaker for many people, I think (including me, sadly because I really want this phone)