I use SIS gels pretty much exclusively, I find they are easy to swallow and digest and don't give me indigestion after a few hours.
Having said that, I'm trying Torque gels at the moment and they seem good as well.
After an hour I swallow one if I'm intending doing over another half hour, then one every half an hour after.
If I'm on a 'climby' ride I try to have one about 3k before the climb starts.
They definitely do give you the extra fuel you need on a longer ride, and I have used the SIS caffeine boost gel towards the end of longer rides - this is amazing stuff ! when you're knackered and don't have anything left in the tank they really do give you a buzz and a short burst of energy.
Eating solid food on the bike (apart from banabas) doesn't work for me at all.
I would say - don't touch the lucozade gels - they are so thick and sickly and seem to be simply full of sugar.
I always 'wash a gel down' with sis 'Go' electrolyte drink, alternated with sis PSP energy drink.
At the end of a long ride, within 30 mins of getting home I down a sis ReGo drink (carbs and protein)
And - at the end of a reeaalllly looonnnggg day I'll have a sis Nocte chocolate milkshake at bedtime (more protein and carbs designed to replenish whats been lost and aid muscle recovery)
I reckon the stuff works.
costs a piggin fortune though !