Ptkay,
I'm using a PocketFMS as a backup unit. Can't beat it on value for money: it is free (and so are the database updates!!! but you get better maps if you pay $50). I chose it after trying out a few demos of comercial software packages as I think it is generally superior even if I forget about the cost. It's also evolving and improvements are added quite frequently. So over time it will always be superior to any self-contained GPS unit. It works well with my iPaq2210 + Holux GR230 package.
Would I use it as a main means of navigation? Probably not but I avoid relying on GPS anyway and use it instead to ensure that my pilotage, dead-rec or VOR/NDB tracking are working out ok. I do like the nav bit of flying and moving-map GPS is too easy and takes the fun out of it. And I suspect it is too easy to become dependant on it to the point you can't find your way without it - sometime ago I met a reasonably experienced pilot who seemed unable to find the way from Elstree to Bovingdon and back without GPS!
In summary, as a backup handheld unit I think it can't be beaten.
Mak