I used to get that message a lot. Since KitKat it doesn't come up, BUT my connection is no better in reality, though rumoured to be fixed in 4.4. When in a public wifi area/Coffee shop I still get the disconnected message below with 5 blue bars (screenshot in a bad area). My GS2 with me connects fine.
Still not happy with wifi, and I tried that trick several times.
Morning All. Since I had 4.3 upgrade I have had Your wifi connection is unstable at the top of my screen. It hasn't really bothered me but I have just cleared the cache and rebooted and it seems to have cleared resolved the issue for now!