Definitely it becomes the opposite once you get over induction flu. The only problems I have once I am adjusted to ketosis (after a week or so on low enough carbs) is when I am doing a long walk (several hours) or doing something over the period of several hours non-stop (like cleaning the house). If I don't stop and have a snack, I sort of bottom out.
I think the problem is that people get a lot of mixed messages about low carb diets from people trying to sell a new take on it or sell some frankenfood products. I think KISS is the best approach. My advice:
-Leftovers for breakfast if you can't stand eggs. The idea that there are "breakfast foods" is cultural. Nuts and low carb fruit (berries, some melon) is also a good option. If you can tolerate flax, flax muffins are quick and easy. Google "revolution" or "oopsie rolls" for another bread substitute.
-Read a book. I really suggest one of the older Atkin books, but there are others out there that are really good. One focused on UK foods is "The Idiot Proof Diet" written by India Knight and Neris Thomas. [Edit: they also have an excellent low carb cookbook. Some incredible recipes in it, and both books are really cheap]. At first you should really try to follow a plan rather than patch things together. You can always experiment later.
-Eat a salad every day. Learn to make your own dressings.
-Don't skimp on fat. South Beach is low fat, so I guess if you're following that, ignore this bit of advice, but almost all other low carb diets are high fat, and there are numerous reasons for the advocates of low carb to press for high fat (generally). Plus, you won't need so much stuff like flax or psyllium if you eat enough fat (and are careful with the dairy).
-make as much as possible from scratch, but it doesn't need to be complicated.
-Eat when you are hungry. Don't eat when you are not.
-if you're doing something for a long period of time, bring a snack
-Try new things.
I am back on low carb (well I have been for a few months) after trying low GI vegetarian. What I was finding was that I wasn't just eating low GI, but was eating really near ketosis levels of carbs naturally when I was making an effort to lose weight. If I am not careful with my sugars (by sugars I mean carbs and not just the white refined stuff), I eat more. The problem was, I wasn't getting much nutrition, and when I figured out my calorie intake, it was way too low to be healthy.
I don't know if low carb is for everyone, but I do know that a lot of the resistance is cultural rather than physiological. I am not going to downplay the importance of the food/culture connection as I think that that has been my problem following through the final push to get to a normal weight range after maintaining a weight loss that is essentially a person in amount. I've lost a person and still fat. I guess I could be discouraged by that, but you know, I think I am just going.
Good luck to those who are going to try it out.
ETA: The reason your energy bottoms out, btw, is your body is basically switching from using dietary sugar for fuels to converting protein and fat to fuel. It's a totally different way of doing things, and is less efficient, so no, you will never get a "sugar rush" when eating low carbs. However, after your body gets used to it, you definitely have more energy and less fog than eating conventionally.
I am going to probably write something more about this in Shrinkers. It's a little personal to get into too much out here.