All these are really nice but I recently had to automatically create bussness partner for users created the same day, so I ended up using a standart FM that uses the BAPI but makes the life a lot easier when supplying the data. I had a UNAME of the user so this is what I used:
TYPES: BEGIN OF ltype_gen,
fieldname(30) TYPE c,
counter TYPE i,
fieldvalue(132) TYPE c,
END OF ltype_gen.
DATA: lt_gen_tab TYPE STANDARD TABLE OF ltype_gen.
SELECT BNAME FROM USR02 INTO ls_gen_tab-fieldvalue
WHERE ERDAT EQ sy-datum.
IF SY-SUBRC = 0.
ls_gen_tab-fieldname = 'UNAME'.
APPEND ls_gen_tab TO lt_gen_tab.
ENDIF.
EXIT.
ENDSELECT.
*---FILL user DETAILS ---*
CALL FUNCTION '/SDF/SOLMAN_GET_USER_DETAIL'
* DESTINATION lf_rfcdest
TABLES
pt_gen_tab = lt_gen_tab
return = lt_return.
*--- CREATE THE BP---*
CALL FUNCTION 'CRM_DNO_MAINTAIN_BUPA_FROM_USR'
* EXPORTING
* IV_COMMIT = TRUE
TABLES
TI_DATA = lt_gen_tab
TE_RETURN = lt_return
So the magic FM is CRM_DNO_MAINTAIN_BUPA_FROM_USR.
I tried to simplify the example code here so read it before running it 
I got this by debugging tcode BP_gen.
And do not forget the authority checks:
AUTHORITY-CHECK OBJECT 'B_BUPA_RLT'
ID 'ACTVT' FIELD '03'
ID 'RLTYP' DUMMY.
AUTHORITY-CHECK OBJECT 'B_BUPA_GRP'
ID 'ACTVT' FIELD '03'.