Since it took me a while to figure this out, I thought it might be helpful if posted this here. Even though this is rather general Iphone (3g) behaviour, it seems to fit here too.
The Iphone itself, and other devices seem to send out a lot of noise, which quickly interferes with each other. If you have wireless home phones, more than one router, plus your iphone I would strongly suggest to optimize the channel usage in your home.
It is always best to choose frequencies which are furthest away from each other. For example if you have two routers, choose channel 1 and 13 (1 and 12 outside Europe). The Iphone itself seems to be in the lower range of these router channels, so I would recommend to set the closest router on the highest possible channel available (13 in europe, 12 outside europe). If you have other wireless appliances around, try moving them as far away as possible, and if you can find out on which bandwidth they operate, adjust router channel settings accordingly.
Some might think that this is not that important, but I just realized HOW important it is. My Intelliphone s' connection improved drastically after optimizing the bandwidth allocations. As well this will improve the range of your wireless devices. So if you keep on having inconsistencies and weird connectivity issues, please try as explained above.
PS: Intelliphone rocks!