No I don't have any personal experience with it, just reviews I've read and stuff like that but I haven't seen any mention of it being particularly difficult to install. From what I have seen I would imagine that it is no more difficult to install than any other 3rd party GPU cooling solution and I would think that if you are comfortable with things like removing the stock cooler and changing TIM then you wouldn't have any problem installing the AXP. There is a user manual available for download here on the product page
for the AXP under the support tab, so you might consider reading through that and seeing if it seems daunting to you.
I like the look of your rig BTW it looks pretty clean. It looks like there is nothing impeding the airflow of that top 140mm to the GPU. If that's true and there's nothing in the way like more drive bays that I can't see then I would suggest just replacing the 140mm for a better one like you mentioned if you feel the need and not adding a fan directly in front of the 580 because it should already be getting good unimpeded airflow from that 140mm and another fan seems unnecessary to me. Also it probably won't make any difference at all but if it were me I would route the GPU power cables above the card rather than below it so there is nothing at all in between the front 140mm intake and the GPU's intake. But only if it doesn't affect the cleanliness of your wire hiding/routing because like I said it probably won't make any difference at all, even less than a backplate would LOL. Edited by juano - 4/1/11 at 8:11pm