Today I set up a Novatel Wireless Merlin G201 GPRS modem on my NetBSD/hpcarm HP Jornada 728.
I found some things in the GPRS documentation are lacking.
(http://netbsd.org/Documentation/network/gprs.html)

First thing I ran into was that you need to turn off PIN request in the SIM card using
a mobile phone.

Second thing, the GPRS provider needs me to set an APN (access point name),
if I don't give it the right APN I won't get the right connection profile.
After googling and finding some linux documentation for a different card I
figured out how that is done.
So my chat script goes like this:

ABORT BUSY ABORT 'NO CARRIER' ABORT ERROR '' ATZ OK 'at+cgdcont=1,"IP","open.internet"' OK 'ATDT*99#' CONNECT

where open.internet is the apn name for O2 in Ireland to give me
an unfirewalled IP link.

Third thing, in my case the provider doesn't automatically configure DNS
so I had to remove the usepeerdns option or else I got an error about
an invalid IPCP message.
pppd[4211]: Received bad configure-rej:  81 06 00 00 00 00 81 06 00 00 00 00

I figure these 3 should probably be added to the GPRS documentation.

Baldur