pH Pen Experiences

Would anyone care to share their pH pen experiences?  I know problems with
these (or similar devices) has been discussed on this list, but has anyone
had good experiences with any particular brands?  How about the Hanna brand
that Daleco and MOPets sell?  I am getting powerfully sick of reagent pH
tests as I try to work out the kinks in a number of CO2 supplemented tanks.