I have never really gotten into the whole shake idea. If i'm in a huge hurry in the morning i grab a smoothie yogurt and a piece of fruit, but I really love my cereal in the morning with the fruit. I dont think i could replace breakfast as it's my most important meal.
I suggest waking up earlier as well. I know it's tough, I go to work at 6:30-7am mon-friday so i get up about 4 am just so i can have my morning workout, a nice breakfast, grab that banana/orange/apple on my way out to work for my midmorning snack. By lunch if i dont have something to actually eat i know i'd find myself at the snack machine, so i can't sub that out.
And with a very hungry hubby in the evening i could never replace that.
Maybe weekends, but then I find that if i dont eat a meal... I'll get bored and want to snack on chips instead of celery and carrots. I'm just not down with the meal replacement stuff.
If you dont have time in the morning i suggest getting everything ready. On thursday nights we go to a lil bar with some friends so i know i'm always rushing friday and only get about 6-7 hours of sleep so i do a quick 10-15 minute workout and have my cereal in a small container, the milk already measured and in a bottle, and the fruit cut up so i just pour the three together in a bowl and pooof breakfast is served!! Just a little hint I guess.. sometimes I find that if i make the breakfast/lunch the day before and label the storage bowl, then I have to eat that and dont try to reach for something different. Helps me sometimes.
Anyway good luck and see ya around!