Really the only issue that I can find with it as it stands today is that occasionally the UI performance is a bit slower than I would want it to be... This is likely due to the fact that neither the integrated Intel graphics nor the nVidia discrete chip were designed to push the 5 million+ pixels of the Retina display.
This was
hugely improved in Mountain Lion, specifically in Safari (I use Safari 6 now for daily browsing rather than Chrome because it actually renders pages much faster and scrolling is smoother), but it's still not 100% there.
Anand has taken a good look at this here:
http://www.anandtech.com/show/6023/the-nextgen-macbook-pro-with-retina-display-review/8
It personally doesn't bother me, and it's noticeable only occasionally, but it's something to keep in mind if you are on the fence. Waiting until next year's refresh might provide some relief in this area if Apple upgrades the CPU and GPU with components designed to push such a high resolution.
With that being said, the machine still performs amazingly and the integrated HD 4000 graphics can handle everything aside from gaming/intensive 3D graphics, so it's not like you need to fire up the discrete chip and burn battery life if you want to watch a YouTube video in fullscreen or something (this is something else that's been improved in Mountaion Lion - the discrete chip is switched to much less frequently).
Only other complaint is that it can heat up your lap quite a bit if you are doing something intensive, but the fan noise and battery life are very reasonable and this is nothing new to the MacBook Pro line...