I doubt you are going to hear much "chatter" on standard GMRS (simplex) freqs. Most of the radio nerds hang out on the repeaters if they are just looking to chat.
You'll still hear those nerds. They transmit to the repeater on the 467.XXX MHz frequency, but the repeater then turns around and transmits on the same 462.XXX MHz frequency as the simplex channel on the same frequency. For example, GMRS 15 (simplex) is on 462.550 MHz for both transmit and receive, but GMRS Repeater Channel 15 is on 467.550 MHz for transmitting, but 462.550 MHZ for receiving, so when two nerds are using GMRS Repeater Channel 15, it goes like this:
Nerd A transmits on 467.550.
The repeater receives the transmission on 467.550.
The repeater simultaneously sends out the received transmission on 462.550.
Nerd B, and anyone on GRMS 15 (simplex) receives the repeated transmission on 462.550.
Nerd B responds by transmitting on 467.550.
The repeater receives the transmission on 467.550.
The repeater simultaneously sends out the received transmission on 462.550.
Nerd A, and anyone on GRMS 15 (simplex) receives the repeated transmission on 462.550.
Repeaters sometimes use CTCSS (analog) or DCS (digital) codes to determine which transmissions to repeat, but if your radio is programmed for "open" transmit and receive (like standard GMRS channels), you'll hear every transmission, so you'll hear all those nerds.