Good points, HTG!
Few more thoughts:
Tolerance for low carbs varies a great deal from what I've seen. I know people who low-carb and feel better in ketosis - literally they would rather be ketotic (they like the ketone-buzz) than eating carbs. I also know people who never really adapt to low / no carbs. They just constantly crave carbs. Many people will fell like shit for the first couple weeks, and then seem to get over the hump.
I have done cyclical ketogenic diets nearly every way I can think:
5 on / 2 off
Carbs 1/2 of a the day 3x/ week on training days only:
4 on / 3 off
5 on / 2 off w/ a "carb-spike" (8hr carb-up) during the middle of the week.
4 on / 1 off / 4 on / 3 off
etc.
I always plan on taking time off the diet as I diet in for a show. Right now, I am doing 3 weeks keto (5on / 2 off), 1 week maintenance kcal (low fat w/ EFA's, 15kcal / lb), 3 wk keto, etc...
Tolerance to the diet is really a very mental thing, I've found. If the week were 10 days long, going for 8 days in ketosis would not be so bad. BUT, anyone who has done the 5 keto / 2 carb standard (bodyopus, etc.) rotation knows that the last day before carbing up is the hardest - you are anticipating the carbs.
For those w/ carb cravings, I recommend doing more frequent carb-ups or even 1 carb meal after training (only). If you know you only have to go 3 days before a carb up, its not as tough as if you have to wait 5. Also, knowing that you have a week "off" the diet coming up is helpful mentally. I do the week off for the rebound effect (I'll gain some muscle during that time) as well as to re-set my thyroid metabolism. This works well, too, if you have an important week at work, etc. when you want to be able to eat more normally and not be as drained from the diet.
-Randy