Well, if you're used to guiness extra stout in a bottle (not sure that's what u were drinking before or not), then guinness draught is definitely going to taste different. I noticed this when i first started drinking guiness (why does the bottle taste good and this pint taste like water?) If you go back to the extra stout in a bottle, you may get back some of your nostalgia, but on tap it's crap. I don't even know why they make guinness draught bottles, (here's the same crappy taste you get in a bar, now you can have it at home too!) And yes, it is really watery. I think your palette has surpassed guinness. It's more of what i like to call a "starter beer", it got you started on the road to better beer by giving you enough flavor to make you think it's really good, but not too harsh to turn you away. then from there, you probably just developed into better beers.
I'll usually order a guiness when i need to stay hydrated, maybe before backpacking through the desert. i'll bring a sixer with me, gotta get that H20 when it's hot; i'm pretty sure Bear Grylls does this ("i'd never 'ave made it off of that glassi-ure without my guiness for hydration")