Strangely enough, I've found that since I increased my caffeine intake (to around 900-1200mg/day via energy drinks) I've been sleeping great. I usually go to sleep around 10pm, wake up naturally around 3am, and take a 1 hour nap around 3 pm. I've been drinking a lot of water as well, and I've had no problems focusing on work. I think the nap is the key though.
How has 900-1200mg/day worked out for you? I considered it a lot when I was doing 500-600mg/day.
I used to get a little heart weirdness (a weird beat once in a while), but I've cut down smoking to 1 or 2 cigarettes per day and started drinking more water and the heart weirdness has stopped happening.