i also have the same problem. its really frustrating..i noticed that the wifi signal for the iphone 5 is much weaker compared to my wife's iphone 4s. i need to be right beside the router in order to connect. if i'm already around 5 feet away it will already disconnect. i already tried network reset, reset of the router and still has the same problem
The difference is that the Apple store (and Starbucks) have professional quality routers, and you probably have a cheap router that may not have up to date firmware. You may also have interference from nearby networks, or from cordless phones or other RF "noise" in your house. It will affect phones more than computers because the phones use lower power than computers so your battery doesn't run down in minutes.
To deal with the interference from other routers, go into your router settings and change channel selection from "auto" to a fixed channel. Do not use channels 6 or 11, as those are the defaults for all new routers.
If you have cordless phones try moving them away from the iPhone and the router.
In any case, update your router firmware by downloading updates from the manufacturer's web side.
If you have a dlink router replace it; they don't work well with iPhones.
If you had a problem with all WiFi networks it is likely the problem was with your phone, but if it works on some networks and not others it is much more likely to be the router.
This morning, I got 10-15+ Mbps on both iPhone 5 and iPad (3rd generation). This was very early morning (e.g. minimal network traffic, interference, etc.) Later same morning, both devices drop to 1-3 Mbps, I assume because there is more wifi activity in and around my house.
Late morning I changed my router channel from Auto to channel 1 as recommended by Lawrence.
Now getting 25+ Mbps on iPad. Interesting fact on the iPhone5, I get a range of 1 Mbps to 20 Mbps. Why such range in results when I run speedtest within minutes of multiple tests?.
My non-technical conclusion so far: Since I have seen the iPhone 5 hit 20 Mbps at times, (though mostly 1-3 Mbps), this to me says its not a hardware issue. The variability on the wifi network is the mystery. Note all other devices (non-iOS) routinely get 20-30 Mbps on my wifi (my cable package is 30 Mbps into the house)
Perhaps iPhone 5 (and our 4s) have less "powerful" wifi capability when compared to iPad, and thus fall to the back of the bandwidth line when the network is busy?
Quick update. I restarted the iPhone 5 and now results are consistently 15-20 Mbps, much better. iPad still gets 25+ Mbps.
At this time the only variable I changed was switching to channel 1 on my home router. (It was set to Auto)
I'll report back later once I'm able to confirm these settings (hopefully) remain positive.