are you getting the stock recovery or SPRecovery when you reboot into recovery?
You can try this update.zip
update.zip its an older version of superuser but it will work just fine
Ah, I'm in the stock recovery... I hold 'x' and it boots to the triangle with exclamation point... I figured you meant press up volume and picture button to go to recovery... should it boot to something else? This is the result of the ./sbf_flash on linux, did it install correctly?:
./sbf_flash -r --recovery SPRecovery_ESE81.sbf
SBF FLASH 1.08 (mbm)
Droid found.
CG63 0xC0000000-0xC001FFFF mbmloader.img
CG30 0xC0020000-0xC00BFFFF mbm.img
CG55 0xC00C0000-0xC015FFFF mbmbackup.img
CG31 0xC0160000-0xC01BFFFF cdt.bin
CG38 0xD01CE000-0xD0359FFF pds
CG34 0xC035A000-0xC03BCFFF lbl
CG57 0xC03BD000-0xC041FFFF lbl_backup
CG41 0xC0400000-0xC057FFFF sp
CG42 0xC0580000-0xC061FFFF logo.bin
CG44 0xC0620000-0xC067FFFF misc
CG35 0xC0680000-0xC09FFFFF boot
CG47 0xC0A00000-0xC0E7FFFF recovery
CG39 0xD0EF4000-0xD9FB6FFF system
CG40 0xD9FB7000-0xDFF3BFFF cache
CG37 0xDFF3C000-0xF0D29FFF userdata
CG53 0xDFD40000-0xDFF3FFFF kpanic
Index[1]: Unexpected chip 16
Index[2]: Unexpected chip 16
=== SPRecovery_ESE81.sbf ===
00: RDL03 0x80500000-0x8054CFFF FE66 AP
01: CG35 0xC0680000-0xC08E37FF ABCB AP boot
02: CG47 0xC0A00000-0xC0D5C7FF 02C0 AP recovery
Skipping CG35 0xC0680000-0xC09FFFFF
>> waiting for phone: Droid found.
>> uploading RDL03
Uploading: 100% OK
>> verifying ramloader
-- OK
>> executing ramloader
Droid found.
>> sending erase
>> uploading CG47
Uploading: 100% OK
>> verifying CG47
-- OK
>> rebooting