In the end, $4,000 for a 300/2.8 just scared me. I just ordered a slightly used 300/4 IS for $1K delivered. Hopefully, it would be sharp and flare-resistant enough...if not, I'll have to sell it and get the 2.8 after all. 300/4 does have 5ft close focus instead of 8, somewhat significant for me. The significance loss of selective focus at range remains to be seen.