Discobaz,
In terms of water flow rate, it works very well for me and I love the system. I have a 45L poly tank wedged behind rear passenger seat (there's a post on this from a couple of years ago with a sketch and photos).
The only niggles are:
1. if you don't use the pump for a while, it flavours the water that's been sitting in it, which is a little disappointing as is supposed to be for drinking purposes. However, not a big issue, before I take the water, I just run a cup or two before first use or if its been sitting overnight.
2. the pump cuts off when you shut the tap but doesn't seem to seal completely and "blips" on and off every 10s or so, which I find annoying. So, I turn the pump on and off with the blue switch you can see in the photo.
3. the outlet barb is a funny size (small) and I had to make a series of step up fittings and hose sizes to be able to fit a reasonable tap on the end of the hose. It may be the issue in 2. is to do with the fittings but I haven't seen any leaks so I assume its the pump which allows a little backflow.

