I'd say this is a very logical feature. I'm surprised it's not already there. My Android phone seems to do this, but not always well. I can't see any reason not to have this happen.
Of course, it would be subject to use preference.
Of course it would be better if the WiFi "just works," but there are many times it doesn't, or it's slow, or the router loses its mind and needs a re-boot.
How does your Android phone or laptop fix the WiFi signal level when you're too far away from the router?
Only one doubt I have is while switching the net connection , if i am in the middle of downloading something ,will my current downloading get aborted and I have to start afresh? Many times such aborting wastes a lot of data already downloaded and the whole process has to be repeated
This is a great idea! If I'm out in the yard, my phone will still connect to the WiFi, but the signal is weak and the data rate is often better on 3G. In those situations, I usually shut off WiFi to force it to use 3G. Then I have to remember to turn WiFi on again when I go back indoors.
I think you guys saying "illogical" are misunderstanding. On the iPhone, WiFi is either on or off and Cellular Data is either on or off, both under user control. When both network connections are enabled, in iOS5 the phone always chooses WiFi if it can. It seems that in iOS6, when both networks are enabled, the phone will choose whichever one has the faster data rate.
This isn't going to prohibit anyone from shutting off Cellular Data to avoid exceeding their monthly data allowance.
Omitted to say, when I say, 'login', I don't mean the connection's password, I mean that a web page will pop up forcing one to either signup for the location's branded WiFi service or if you're already signed up, login. You cannot remain logged in because the connections often have time limits.