Most people want Lee Filters, but get frustrated because they're on back order. You can add your name to the list of people waiting for theirs to come. I have managed to get my hands on their 3, 6, 9 Neutral Density set as well as their 3, 6, 9 Graduated Neutral Density set, the square full red, and the sunset set (half red, half orange, and half yellow.) I also have a Tamron half red and a Tamron half blue. In addition, I have a whole bunch of home-made filters, but that's another post worth of information.
While using a filter, I can indeed produce a SOOC (Straight out of camera) image that is (from my perspective) better than the one I could produce with layers in photoshop with no filter use. I also find that to properly use LEE filters, one needs to know how to use the white balance on their camera to better amplify the effect of the filters (or you can do it with software, but that doesn't typically turn out as nice). What I'm saying is that when you use filters, you're better off NOT shooting on AWB.
Lee is the top-of-the-line company, but if you don't want to wait or don't want to pay that much (remember that a British Pound is currently $1.55) here are some you could substitute as kits: HiTech, SinghRay, Tamron. Don't substitute Hoya or Cokin. Honestly I think my Hoya is best used as a Frisbee. Cokin only produces graduated color filters, and there is a big difference between that and a graduated gray filter. I can't speak by experience about their quality, as I don't use their products.
Things I like about LEE: they are very compatible with my light meter. Some others I have borrowed have done wacky things to the light meter that make it annoying to shoot - you basically have to guess and check on exposure until you get a feel for whether it sits at +2 or -2.
Like all filters, Lee's products are not scratch proof. However, they come in a great cloth case and cardboard box. You can buy their filter pouch for like $7 and that's well worth the price as well. The square ND filters are best kept in the cardboard box. Don't screw up that box!
I don't have much negative to say about the filters except I wish they weren't so hard to obtain.
I will also say that the LEE grad colors out-perform my Tamron grad filters. However, if I tweek my white balance, I can achieve the same result with the Tamron product as I could with the Lee's.
About my LEE Holder
It is larger than other companies' holders, which is very convenient. It holds larger filters (4"x6"), and is great construction. I love the quick release! I can take it off the 77mm (filter size) ring and put it on the 82mm easily and quickly. It's also drop proof by the way.
I wish the attachment (the part that the quick release releases from) screwed onto the lens like either a lens cover or filter does. It's kind of a pain in the neck to attach to my lens quite honestly. It's so much of a pain that I wish I could just leave it permanently on my lens - but if I leave it on and release the holder, I have to take it off to use a lens hood or a filter. It's more than a little annoying, and I have seen better schematics on my friends' cameras.
I wish it had a slot for three filters instead of two (they make a part you can add on, but it's always sold out so if you want to use three filters and have one stay tuned as I am making something and will blog about it once it works the way I need). I find myself sometimes hoping I could use 2 grad colors and an ND but I can't because there are not enough slots to hold them. If someone can find me a 3 slot LEE holder for sale that is not sold out I'd sell my 2 slot holder.
I wish there were a way to use the LEE holder with a circular polarizer on the lens. They sell a "circular polarizer front mount thread" but is back ordered (of course.) I am going to attempt to make one of those as well from a step-up ring.