I just got a Refurb SP 2730 and had a similar problem to Radman. The unit came with NT2008 (which I assume was released in 2007) on the CD in the box. The unit itself has v8 (from 2006) loaded already.
I registered the unit online, and it shows that what I unlocked with the included codes was v8, but it also shows that the unit had previously unlocked another instance of v8 AND an instance of NT2009 (released and registered 2008). So on their site, I am seeing product codes and unlock codes for 2 copies of NT v8 and one of of NT 2009. There is a link to download NT 2009, but it is "expired" and not available for download.
And every time I start MapSource, it says that I have NT 2008 maps installed, but they are still locked.
So I called Garmin. I waited on hold for... well, I think it more than 45 minutes. I was warned that it would be more than 30 minutes at the beginning of the call. Good thing I had a hands-free headset so I could do other stuff while I waited...
Anyway, when I finally talk to someone at Garmin, he is completely confused by the situation. I told him if he could just get me the NT2009 software - without any codes, I would be all set because I've got the codes right in front of me already. He says the unit is not eligible for any free updates, so I have to deal with what was on it. I said I am not happy about buying a device and having to deal with 3-year-old maps, and not being able to sync the maps on the device with the maps on my PC. He tells me to email him my receipt and he'll get someone to help him figure it out. I did so...
About 3 hours later, I got an email in which he basically says "I'm not supposed to do this, but I'm sending you NT2010."
OK, I'm good with that!
Not what I was expecting, but I won't complain about Garmin going above and beyond for once. I Paid $120 for the detailed maps back in 2005 for my little GPSMap60C (which came with no detailed maps at all, despite it's $400 initial cost!), so I feel like maybe now we're even.
I certainly can't expect them to do that for everyone, but I will say that it may be worth waiting on hold to talk to them about any issues. Honestly, I was pleasantly surprised at the outcome here. I figured the best I was going to get was the codes for the NT2008 software that I got in the box.