Heya,
$499 is high for this lens these days. It's pretty aged. 2 stop IS. It's only F4, so it's not the super F2.8L version which still fetches over a grand. But this is no doubt an excellent lens. It's not a Canon big white. But it's an L in every regard. It's light weight, easy to carry, good build, fast AF, sharp wide open and has 2 stop IS which is at least useful when focusing if not helping with that one or two stops of light to avoid pushing ISO real hard. It also allows pretty close range focus which is not common on all "telephotos." You can focus very close with this one. I use a 300 F4L IS and its glued to my 1D3 for wildlife and birds. Takes a TC real nice too (420mm F5.6) and still is pretty sharp and fast to AF. I bought mine from KEH.com with a coupon, and paid around $450, but I was willing to pay that because of their 180 day warranty and guaranteed condition. Buy used without any guarantees, I'd go lower only. It's an old lens and if anything is wrong, likely hood of a fix is low to impossible.
I got a generic tripod collar and it's fully metal, same color paint, fits perfectly. Lots of these on the bay. But generally, I find it's not needed as I usually am hand holding, this is a light lens.
+++++++++++++++
+++++++++++++++

IMAGE LINK: https://flic.kr/p/2cZYsYN
X10S1019 copy
by
Martin Wise
, on Flickr
Love the micro-contrast of the coatings (they're modern, but not the latest nano stuff)
IMAGE LINK: https://flic.kr/p/SVXkoj
9V9A2322 copy
by
Martin Wise
, on Flickr
AF speed kept up with this species, if you know what this is:
IMAGE LINK: https://flic.kr/p/2dyS75t
9V9A1689 copy
by
Martin Wise
, on Flickr
Close range Tern with 1.4x TC:
IMAGE LINK: https://flic.kr/p/Y5RDM6
9V9A9871
by
Martin Wise
, on Flickr
Close range focus is one of it's perks too:
IMAGE LINK: https://flic.kr/p/YHej1u
9V9A9940
by
Martin Wise
, on Flickr
Very best,