This plugin is amazing. Since buying it it has helped me achieve better resulting mixes on a few projects.
I only tend to apply about 2-3 dB of the filter to get rid of any harshness and this certainly helps create a more 'analogue' warmth. The solo function is fantastic as it lets you hear exactly what is being removed from the original source.
I don't often write reviews on things but his one deserves it. It's not an 'in your face' effect but if you bypass it you certainy notice the difference. I have tried recreating this effect with various EQ's but it just doesn't compare.
I grabbed it when it was on sale and I have never regretted it. I use it mostly when mastering but I have also used it to tame down the harshness on tracks in projects. One example was doing some post production work for a client's video of a school choir. The audio from the cameras microphone was extremely bright and harsh. This plugin helped tame that source audio sufficiently without losing any of the useful high frequency information.
As their website suggests, grab the software and give it a go for yorself. You may be pleasantly surprised.