The filter is really good, it seems to be a real 10 stop filter (some ND1000 are only 8-9 stops, which makes shutterspeed calculations hard), it is reducing light in both Visible and Infrared light (has been tested on a full spectrum camera used for Infrared Photography), so you will not have a nasty discolouration in the sky as with other ND filters, but you will get a slight blue colour cast, nothing that can not be fixed in post process with the white balance tool, but I highly recommend doing a white balance setting with the filter on to get accurate colours, especially if you are shooting in JPG. I did not see any reduction in detail (see the 100% or 1:1 crop). It easily screwed on my lens and step up rings as well. It has a nice grippy area which I find giving a much better grip than other filters. One thing I'd like to mention is the case it's coming with has a nice locking mechanism and also two carve outs to be able to easily remove the filter from it's case, actually it's one of the best cases I've seen, beating the nice metallic cases from Gobe, which does not close well with larger filters.
If colour cast is a critical issue for you then this filter might disappoint you with it's blue cast, in that case I recommend Haida's NanoPRO ND1000, which I unfortantely lost, but that has virtually no colour cast at all, but nearly triple the price.

For the price the K&F Concept ND1000 is unbeatable. It has just a very very slight blue colour cast, great IR filtering, true 10 stops and no reduction in picture quality. If you are on a budget and looking for an ND1000, look no further.