I knew a little about Tsukihime and nothing about Kara No Kyoukai except that supposedly the movies were good, so I decided to give this a look.
At first (after watching just the first movie) I felt like it had a ton of unnecessary explanation and abilities that I had no idea about. Questions in my mind:
"What kind of convoluted explanation is that? Isn't it simpler if...?"
"How the hell did she do that? Was that even foreshadowed?"
I didn't think movie #1 stood very well by itself (however awesome the music and action was).
Then I continued watching...and by the 3rd movie I had a more favorable impression as the Kara No Kyoukai world was being built across movies. I think at this point I got into a better mindset for watching - instead of expecting 7 movies, I'm watching 1 very long movie where the important details are scattered throughout each chapter, or where I had to draw my own inferences because the movies neglected them.
My personal high point was movie #5 where a number of threads finally came together and I had a better idea about what was going on - after some rewatching. This seems to be one of those series where subsequent views let you see details you missed on the first time through.
Production values are high throughout the series. Backgrounds are beautiful and dreary, animation is smooth, and music tends to be appropriately epic.
Personal taste: I sort of wished some of the scenes weren't as graphic. Movie #3's opening and some parts of movie #5 and movie #7 stood out in my mind (my recommendation: do not eat while watching movie #7).
I really didn't like some of the philosophy in movie #7 either but I'm a pretty devout pragmatist so your mileage may vary.
Overall? I came away quite satisfied watching this. I recommend a watch, assuming you don't mind doing lots of thinking and aren't put off by having to watch (and possibly re-watch?) 7 movies.