As a shock pump, I quite like my Specalised Windpipe Shock http://www.evanscycles.com/product.jsp?style=12001 It also pumps up tyres (not that well, but no worse than micropumps) so is great for those 'take two bottles into the shower' moments......
I had a Topeak Master Blaster and it was shit, always leaked air when you took it off the valve. So you never really knew what pressure you were running.
Lots of them are high/low pressure specific. i.e. for rear shocks or forks.
The gauge, on the same pump will only be accurate with itself, there is no magic formula just a approximation for your weight anyway, so it's not a issue.
220psi on my pump, is always the same, thats all I care about.
For Floats low or high pressure ?? I know the Talas's are low, so could need 2 pumps really.