We take in account the SOI in our decision making on ENSO status.  Believe it or not even the BOM page says it's quite negative at the moment!   However, it's important to keep in mind one of the reasons that the "traditional" SOI exists is b/c it was established well before the current era where we can measure SLP over the entire global oceans with reasonable accuracy.  Back then they had to find two weather stations where they could measure ENSO!  Given the lack of land sites in the Pacific, they picked Tahiti which is almost 20degrees latitude in the Southern Hemisphere.  For this reason, we often rely on the newer "Equatorial SOI" which is located on the equator, arguably more central to ENSO dynamics.   This index has been more firmly negative over the past several months.  The traditional SOI still has its value (a long historical station based record), but for monitoring we also strongly consider the Equatorial SOI in addition to other atmospheric measures (precip/OLR/winds/etc).