PB's and great runs galore at the weekend, paricularly DrDave with a monster run!
I've joined the benched with sickness team(cold with laryngitis) and have not run since Sat. We're moving to Devon on Monday so there's much to do around the house. This plus still being tired and achy = long lay off. Bugger.
I ran a PB at London last year using only lucozade sport and had no issues with it at all. My stomach is very sensitive when working hard. I did finally find gels that were ok : Torq gels. Taste good too
Muss - I would experiment lots with different gels, shot bloks, drinks etc. Find out what you can stomach and stick with it. Also, taking them on a leisurely run won't give you an idea of how your system will tolerate it when it's working hard. Took me ages to find something that agreed with me (Torq gels for the record). I aim for one every 5 miles up to 20 but have only ever got two down and then drunk lucozade or whatever was available.
Having said that, training and honest assessment of fitness are by far the most important factors in my opinion.