[Xperia Play Q&A, Help & Troubleshooting] vokal1992:
I can confirm that the System partition does in fact install and boots fine, but I allways get Keyboard FC's and alot of stuff didnt got installed :S

Edit: here is the Build.prop, found some funny things:

##### Merging of the /util/data/semc_kernel_time_stamp.prop file #####
ro.build.date=Thu May 24 16:12:14 2012
ro.build.date.utc=1337868734
ro.build.user=BuildUser
ro.build.host=BuildHost

##### Final patch of properties #####
ro.build.product=MT25i
ro.build.description=MT25i-user 4.0.4 4.1.B.0.479 IL5_3w test-keys

ro.product.brand=SEMC
ro.product.name=MT25i_1265-5721
ro.product.device=MT25i
ro.build.tags=release-keys
ro.build.fingerprint=SEMC/MT25i_1265-5721/MT25i:4.0.4/4.1.B.0.479/IL5_3w:user/release-keys

######################## Customized property values #########################

ro.semc.version.cust=1265-5721
ro.semc.version.cust_revision=R2I
persist.ro.ril.sms_sync_sending=1
ro.settings.apn.lock=ä¸*å›½ç§»åŠ¨äº’è”ç½‘,ä¸*å›½è”é€šäº’è”ç½‘,ä¸*å›½ç§»åŠ¨MMS,ä¸*å›½ç§»åŠ¨WAP,ä¸*å›½è”é€šMMS,ä¸*å›½è”é€šWAP

#########################################################################

ro.config.ringtone=xperia.ogg
ro.config.notification_sound=notification.ogg
ro.config.alarm_alert=alarm.ogg
ro.semc.content.number=PA1

################# Updating of the SW Version #################
ro.semc.version.fs_revision=4.1.B.0.479
ro.build.id=4.1.B.0.479
ro.build.display.id=4.1.B.0.479

##### Values from product package metadata #####
ro.semc.product.model=MT25i
ro.semc.ms_type_id=PM-0110-BV
ro.semc.version.fs=WORLD-i
ro.semc.product.name=Sony Xperiaâ„¢ neo L
ro.semc.product.device=MT25
ro.product.model=MT25i

# begin build properties
# autogenerated by buildinfo.sh
ro.build.version.incremental=IL5_3w
ro.build.version.sdk=15
ro.build.version.codename=REL
ro.build.version.release=4.0.4
ro.build.type=user
ro.product.board=
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.manufacturer=Sony Ericsson
ro.product.locale.language=en
ro.product.locale.region=GB
ro.wifi.channels=
ro.board.platform=msm7x30
# ro.build.product is obsolete; use ro.product.device
# Do not try to parse ro.build.description or .fingerprint
ro.build.characteristics=default
# end build properties
#
# system.prop for phoenix
#

# Notify the system that the RIL only signals once
ro.telephony.call_ring.multiple=0

rild.libpath=/system/lib/libril-qc-1.so
rild.libargs=-d /dev/smd0
persist.rild.nitz_plmn=
persist.rild.nitz_long_ons_0=
persist.rild.nitz_long_ons_1=
persist.rild.nitz_long_ons_2=
persist.rild.nitz_long_ons_3=
persist.rild.nitz_short_ons_0=
persist.rild.nitz_short_ons_1=
persist.rild.nitz_short_ons_2=
persist.rild.nitz_short_ons_3=
DEVICE_PROVISIONED=1
ro.semc.timescape_keys=Sony_Ericsson_Xperia_PLAY
#Automount restored because of the exclusion backcover HW key operation.
#ro.product.sdcard.automount=0
ro.semc.sols.product-code=107
ro.semc.sols.company-code=5

# Disable strict mode checking
persist.android.strictmode=0

# Constant values for Battery test in Service menu
ro.semc.batt.capacity=1500
ro.semc.batt.test.z_threshold=50
ro.semc.batt.test.min_level=70

#Default values/Locales for the hiding languages feature
ro.product.locale.excluded=ar_EG ar_IL fa_IR iw_IL

#
# ADDITIONAL_BUILD_PROPERTIES
#
ro.product-res-path=framework/SemcGenericUxpRes.apk
ro.setupwizard.mode=DISABLED
ro.com.google.gmsversion=4.0_r2
ro.com.google.clientidbase=android-sonyericsson
drm.service.enabled=true
keyguard.no_require_sim=true
ro.com.android.dateformat=MM-dd-yyyy
ro.com.android.dataroaming=false
ro.ril.hsxpa=1
ro.ril.gprsclass=10
ro.semc.xloud.supported=true
ro.sf.lcd_density=240
dalvik.vm.heapstartsize=5m
dalvik.vm.heapgrowthlimit=48m
dalvik.vm.heapsize=128m
wifi.interface=eth0
wifi.supplicant_scan_interval=15
ro.semc.dashboard.xperiaplay=true
ro.semc.dashboard.searchuri=http://pss.dl.playstation.net/pss/content/list.html
ro.usb.pid_suffix=17C
dalvik.vm.dexopt-flags=m=y
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt
ro.drm.active.num=4
ro.drm.active.0=semc,1
ro.drm.active.1=cmla,0
ro.drm.active.2=viaccess,0
ro.drm.active.3=marlin,1

Also found some xperia play stuff on framework

Going to update my NeoS rom with these :P