They're only $900 new at Costco, so it's not a $4-500 price dif, but I digress.
http://www.costco.ca/Browse/Product....152&lang=en-CA
Not saying the refurb isn't a good deal, just suggesting that my biggest worry would be the bulb. Reading the ebay listing, he's giving the specs for that projector model, not that specific re-furb. May be worth asking if the bulb is fresh.
Keep in mind that '4000' hours life generally isn't under real world conditions. It'll probably translate to half of that.
Looking around the bulb is only $220. So you're only $20 out if you have to replace it anyways. Go for it.