I just did my first run with my vest, the Scott Jurek (mid capacity) version.

Overall, I am very happy with it.  My biggest gripe is the bottles.There is a rubber nipple that you have to extend and bite down on, and you still need to squeeze the bottle fairly hard.  And when you squeeze, the bottle leaks from around the cap.  Not a lot, but it seems wasteful.

I carried one of the UD 20 oz bottles on the right, and on the left I used a small Amphipod bottle plus my Samsung Galaxy S4.  With the grippy rubber removed from the phone, it slipped in and out super-easily and yet felt very secure due to the drawstring.  I started the run with the phone next to my body, but it was getting too steamed up - lost some good pictures (boo!)  After switching the phone to the front of the bottle it was perfect.  Also, the phone did fit with the protective cover on, but because the cover was so grippy it made it difficult to insert/remove.

I ran a 27 mile run with 4 major mountain passes, so I got to stow/remove trekking poles several times.  Having a dedicated means to carry poles is very nice.  (The Peter Bawkin vest has a different system that I couldn't figure out; IMO the SJ vest system is much nicer.)  While running, I was able to forget that the poles were there, and not worry about losing them.  Yay!

One quibble about the T-pole carrying method is that it blocks access to the rear compartment zippers.  To get anything in or out requires unhooking the shock cord from the little hooks, and that's a bit fussy.  No big deal for a fun run, but in a race it could be frustrating.  I can't help thinking a much better solution exists.

Capacity-wise the pack is great.  I carried a base layer top, a rain shell, a 20 oz Gatorade bottle, map, bike gloves, enough gels/bars/pills/iodine for 11 hours of "running", plus an additional 2000 calories of cookies and trail mix that I did not need.  And I could have stuffed quite a bit more in.

As mentioned by others, the lower side pockets are pretty far back.  I think this will depend on your body size and which vest size you choose, as there is no adjustment for the sides/rear of the vest.  I carried 3 packs of shot blocks and 2 Cliff bars in those pockets, and was able to remove them with the vest on, but it took some concentration. I suspect it will get a bit easier with practice.

I think the location of those "side" pockets is probably just about right, though.  If they were directly on the side of your ribcage, even a very small amount of cargo would probably interfere with your arm swing.  As it was, I had no discomfort or interference at all.

One particular nicety is the pill pockets beneath the water bottles up front.  I used one for water purification tablets.  So nice to be able to just reach and grab them without having to search around.

I used to scoff at the high prices people pay for silly running knick-knacks, but in this case I think the money goes toward some very, very thoughtful design and top-of-the-line materials.  The pleasure and convenience this provides ,IMO, make it worth it.  Despite the minor gripes noted, I am very happy with my purchase.