Using GT-I9100 in USA

[Michael Spacefalcon]

Hello list,

Following the recommendations I got here and my own gut feeling, I
have bought a Samsung GT-I9100 (Galaxy S2 international GSM version)
with the hope of running Replicant on it.  (I saw the announcement
that the S3 now works just as well, but the micro-SIM slot is a
turn-off for me: all of the SIMs I have available for testing and
experimentation are of the traditional mini-SIM form factor, and I
have no desire to put them under an X-Acto knife.)

I have not yet got as far as attempting to install Replicant, I am
first trying to establish a "baseline" by gettting the device to work
as a phone with its original sw, and I'm having terrible woes which
I'm very much afraid may point toward some nasty incompatibility
between the modem fw (which Replicant wouldn't solve) and my
geographic location.

Because I'm going "against canon" by using an international phone in
USA, communities like this one are the only place I can think of for
turning for help, hence me asking here even though my issue isn't
strictly on-topic as I haven't got to trying Replicant yet.

To the best of my understanding, the I9100 should be able to work in
USA in 3 possible modes:

* on AT&T GSM/EDGE;
* on AT&T UMTS/WCDMA/3G;
* on T-Mobile USA in GSM/2G/EDGE mode.
(T-Mobile USA 3G/4G won't work because they need 1700 MHz uplink)

My ideally-preferred mode would be the last one, namely T-Mobile USA
in GSM/EDGE mode: I have no need for data speeds above EDGE, I have a
religious objection against UMTS &co and prefer classic GSM as a
matter of philosophical principle, and I and my covenmates all have
T-Mobile SIMs, hence having the device work on the T-Mobile network
would be preferable, although having the phone roam on AT&T with a
T-Mobile SIM would also be OK.  (Whatever their roaming agreement is,
we as the users don't get charged for that roaming.)

The problem I'm having is that this I9100 (running whatever sw it came
with, but I very much fear that the problem is in the baseband) seems
to be consulting some psychic oracle to decide whether it should work
or not.  There seems to be some kind of "coin toss" that occurs at
boot time...  On some boot cycles the phone behaves just fine: sees my
SIM card (tested both T-Mobile USA and Telestial), registers with the
T-Mobile network in EDGE mode, and then works beautifully afterward:
voice calls, SMS, data - was even able to watch a YouTube video over
EDGE in this state!

But on other boot cycles (more often than not, in fact) some part of
the sw stack (the modem, I'm afraid) gets into some kind of wedged
state.  The visible symptoms are:

* The phone spontaneously enters "flight mode", but in an erratic
  manner.  If I as the user explicitly turn the flight mode on, an
  airplane icon appears in the place of the cell coverage indicator.
  But in this erratic state the no-coverage icon appears there
  instead.  I only discovered that the phone is in some state such
  that the AP software thinks it's in flight mode when I took a closer
  look at the menu that appears when I hold the power button down to
  power the phone off for reboot.  The spontaneous "flight mode on"
  state also shows up in the "Wireless and network" menu.

* Once in that spontaneous pseudo-flight mode, the device does NOT
  simply stay there "solid".  Instead it occasionally pops in and out
  of that state in a seemingly-random manner.  If I stare at the home
  screen, I can occasionally notice the no-coverage icon change to an
  icon with some bars, then back to no-coverage a split-second (or
  sometimes a full second) later.  If I do this idle watching while in
  the "Wireless and network" menu, I also see the "Flight mode"
  checkbox go on and off on its own, and the "Bluetooth settings" and
  "Mobile networks" menu items gets greyed out or restored in sync.

* If I watch the "Status" screen under "About phone", I see a little
  bit more info.  When the icon at the top goes to no-coverage because
  of this pseudo-flight mode, the Status screen reports "Service state"
  as first "Out of service", then "Radio off".  The "Signal strength"
  shows "0 dBm 0 asu", which is obviously bogus - as if the modem is
  simply not reporting any valid values to the AP.  The "My phone
  number" field usually stays at "Unknown" in this state, even though
  the SIM with the number in it is present all along.

Needless to say, the device is not usable as a phone when it's in this
strange wedged state - and it enters this state on every other boot
cycle or so!  On some "wedged" boot cycles I have observed that poking
at the device (for example, watching the "Wireless and network" menu
screen, catching a moment when the "Mobile networks" submenu gets
re-enabled, going into the latter, selecting "Network operators", then
picking AT&T or T-Mobile) causes it to leave the wedged state and enter
stable operation, as if it had a "happy" boot cycle.  But on other boot
cycles the device remains wedged no matter what I do.  I also haven't
done enough long-duration tests to see if the device ever enters the
wedged state some hours after it had a "happy" boot...

The device is clearly not fit to be given to a non-technical end user
(which was/is my end goal in all of this) when it behaves in this
manner, and my spirits are low...

Hence my question to this list: is there anyone here in this community
who successfully uses (or has used) an I9100, or any other Replicant-
supported GSM smartphone, anywhere in USA, on either AT&T or T-Mobile?
If so, what has your experience been?  And if there isn't anyone in
USA, what have other people's experiences been with I9100 in other
countries?

Here are the sw/fw versions my I9100 currently reports in the "About
phone" menu:

Model number: GT-I9100
Android version: 2.3.3
Baseband version: I9100XXKL1
Kernel version: 2.6.35.7-I9100XXKL1-CL783870 se.infra at SEP-64 #2
Build number: GT-I9100-eng 2.3.3 GINGERBREAD XXKL1 test-keys

I'm not sure how "pristine" or not this phone is: the ebay seller from
whom I bought it listed it as new, but it came rooted: there is a
"Superuser" app present.

TIA for any clues,
SF

P.S. If someone can help me bring this I9100 into a state in which it
works reliably on T-Mobile USA EDGE with T-Mobile USA SIM cards - by
finding and flashing the right "magic" baseband version or whatever -
I will gladly send that person $500 USD.  This is a serious offer, not
a joke.  Offering cash bounties of this kind is my way of supporting
Free Software - FOSS developers should be able to make money selling
support for Free sw instead of proprietary sw.