That happened a lot, but also on every other model phone — AT&T had dramatically underprovisioned their network and 2G and 3G were less efficient at connection setup and supported fewer clients as well.
I wouldn't be surprised if they tried to blame the phone hardware but given every other interaction with that company I would default to assuming someone got a bonus for “saving” money on network capacity and then had to play damage control for a couple of years. My previous phone only had sound quality as good as the iPhone because I had unlocked it and enabled the higher-bitrate standard GSM codecs which AT&T's default policy had disabled.
(IIRC the iPhone issue was hypothesized to be related to an incorrect GSM power management implementation.)