I tried adding a pair of OMM i-Gamy bottle holders, with their specifically designed bottles to the front of my OMM Last Drop, which in theory is designed to work well with them - it has all the gubbins to connect, etc. Started running, kept hitting myself in the fact with the bottle tops, so emptied one and stuck it in the pack, handheld the other. Most annoying.
Currently using a 2l bladder, but reckon it's a faff to refill once inside the bag. Ran the Kielder Marathon with a handheld and a pouch to stick it into on my belt - that worked fairly well, but the further I run, the less I like handholding anything.
Think if the bladder / Last Drop combo was less of a pain to refill, I'd be happy with it, but as it is I don't think I've found the right solution (for me) as yet. May have to learn to run balancing a jug on my head, or maybe one of those beer hats?