Sigma 105mm f2.8 macro lens - is this a promo, or what?

[ultrarunner]

Hey guys;
I'm looking to buy the Sigma 105mm f2.8 EX DG OS HSM Macro lens for my Nikon D200.
The cost is $569 regardless of where I buy it (B&H is my usual go-to). I see that the 'regular' price is $400 higher. One site I visited states the current price is good only until May 02.
Does this lens normally sell for over $900? if so, I definitely want to grab it now.

Next question:
Adorama shows same price as B&H, but they also offer a kit with three Tiffen filters + lens cap keeper, and a cleaning kit - at no additional cost. Unfortunately, they don't have the kit in stock.
I have always steered clear of such freebies, as they are most often junk, and I don't want to put a junk filter in front of a good lens.
At B&H I see the B&W filters, which I understand are superior. But being an amateur, would I notice any difference between the B&W, Tiffen, or Hoya filter?

Thanks for your help
Ultrarunner

Edit:
Anyone know the difference between the B&W 'Nano' and the regular UV filter?
In the description for the Nano, it says an additional (8th) coating is added to repel water and make the filter easier to clean. It also states that the outside ring is slightly larger than the thread dia to reduce chance of vigenetting - but also that it may prevent lens hood from being attached.

Is this going to be an issue with the Sigma 105mm f2.8 macro lens I am looking at?
I always keep the UV filter on the lens (when I'm not using another filter), so I wouldn't want it to interfere with the use of the lens hood.