After extensive testing, I have now adopted Toodledo because the iPod and iPad versions integrate very well with their Web version. Synchronisation appears to be absolutely reliable and *very responsive*.
I switched my personal calendar system to Toodledo from GCal for similar reasons.
Having items in TD strictly identifiable as "calendar items" needs some discipline.
In my case, calendar items are the only ones in which I use the time/date fields, and I always use THE four fields: startdate, duedate, starttime, duetime. I know that they are not intended to be used that way, but most calendar systems "understand" TD events with this workaround. Awkward and unfriendly, but I need it and it is worth sticking with TD.