On your d-link, what was your setting for encryption? WPA/WPA2? I found that after I enabled any WPA encryption that my 3GS had horrible connectivity issues - would constantly drop. No other devices (including my old 1st gen iPhone) would have this problem. After some googling, I found that there is some compatibility issue between the implementations of WPA on iPhone/DLink. Both blame the other, of course... After switching over to WEP I've not had any other problems. Though it's not as secure, it's better than nothing. (Which, by the way, I had no problems with either!) ;)

@Chris: same story here, I could never get a reliable iPhone connection with WPA on the D-Link. I had to use WEP too. It just recently started doing something weird on the iPhones with connecting and then dropping and giving me a "wrong password" prompt, so I decided to retire the old router.

I didn't really worry about the "weak" WEP encryption for my home LAN either, I just wanted to keep the neighbors off my wifi.

I hear ya - glad I wasn't the only one. I saw a lot of chatter in forums about the "wrong password" thing too. But I'm not going to say it's Apple's fault b/c they're always right! :P

LOL. Yeah, I've had that pesky intermittent iPad wireless connection issue too ( http://support.apple.com/kb/TS3304 ) before I started having the iPhone problem, but Apple said that was my fault, not theirs. Hence a new router.