I got my N900 from Vodafone with product code 0595421, I have already reflashed my device and am now using firmware - 10.2010.19-1.203.1. I am unable to see the update via OTA, NSU or Ovi Suite. I spoke to OviByNokia on twitter asking why I am unable to see the update, they responded by saying -

"N900 update not available yet for all codes. Check App manager -> Update just in case. New codes will be added, hopefully soon."

I then asked if there was an ETA for the update to become and they responded with this -

"No specific ETA, but you shouldn't be kept waiting long. You can use http://bit.ly/dDm0XD to find the latest version for your code"

I'm hoping Nokia releases the update sooner rather than later.