Comp Formulas
I derive the 1 unit per hour formula from the premise that Vegas casinos (and casinos in other locales that comp similarly) typically comp about 20% of their expected win. I can't cite an authority for this 20% figure off the top of my head, but I recall reading this in posts on several boards from persons more knowledgeable about comps than me (for what it's worth, Henry Tamburin says the range is 20%-40% - (Dead link: http://www.casino.com/blackjack/article.asp?id=356)).
Of course, they start with the premise that they have a 2% edge against you, which would be true for the average ploppy. If you really have a 1% edge against the house, you'll need to rathole around 7 units per hour, on average, for them to continue to assume you are a typical ploppy over the long haul.
In my green chip days, I usually had little trouble getting comps worth the equivalent of $100 for 4 hours of play (a $79 room, a dinner at a moderate or high-end restaurant, and a buffet lunch will put you well over $100 in value), which would equate to one $25 unit per hour. I generally don't like to put in more than the requisite 4 hours per day at any one casino for the usual reasons.
Results, of course, will vary enormously from casino to casino, and even from PC to PC within the same casino - in some stores you have to fight for a buffet comp after one hour with an average bet of $60 or so. In other stores, I have gotten $75 dinner comps at high end restaurants (think monstrous $45 steak at 9ine at the Palms - can't tell you whether that would still be doable there) for an hour of such play. Note that they are also more likely to throw these comps at you when you're losing -- losing sessions are good times to be a comp monger.
I now play at the black level, and thus far I have gotten pretty much whatever I ask for. I'm not a real comp whore, however, so I haven't really pushed the envelope to see if I could get $400 in comp value for 4 hours of play (with one notable exception -- a plush Caribbean casino has given me a free room worth over $300 and $150 in meals per day - a free Caribbean vacation beats the hell out of anything in LV). Anywhere in the US, getting a $129 room and whatever I want to eat is a given. At some point, I'll have to try to grab a pair of $95 show tickets or a $150 massage and see what happens. When I'm by myself, which is usually the case, I don't want to waste valuable playing time with Celine Dion or Cirque De Soleil, or even with a 7-course meal that takes 90 minutes. I'll need to bring the wife (who, unfortunately, DOES enjoy expensive stuff) in order to really push the envelope.
Regionally, my experience is that comps are easiest in Mississippi (comp heaven for green chippers). LV is next, and AC a bit harder (but improving significantly since the Borgata opened and created actual competition). Generally speaking, you have to play big and lobby hard for your comps in the Caribbean, but it's worth the effort if you can make it happen.