Good to see more choices in the field. To state Hall's somewhat undiplomatic points a little differently, having come through the early stage of LiPo technology many of us in the hobby treat charging these cells as a fairly delicate process.
The "black box" nature of these chargers can leave you a bit worried about what's really going on. Now, to be sure I trust the charge circuit in my phone, laptop, iPod, etc. to get it right without needing any feedback, but flight packs are pushed much closer to the edge in every way.
I'm sure that you'll have plenty of customers that are happy to treat charging their packs as a set and forget operation, but I know that for certain I would pay twice your asking price for your 4-port charger if it had a display that would tell me the current cell voltages for each cell connected, as well as the current taken in by each cell during charging.
One other issue with this charger is the parallel charge leads you offer; if they were available pre-assembled with connectors for the popular pack connectors (TP, Polyquest, Tanic, etc) this would make your unit very attractive.
Finally, you may wish to consider the charger mentioned in this thread: http://www.rcgroups.com/forums/showthread.php?t=315666
The auto-current selection technology it uses is very interesting from the black-box perspective, as well as from a safety perspective even in the manual-setting case.
One final note; you mention one of your chargers has an auto-cell-count detection mode, with an option to override the cell count detection and force charging. I think this was a bad idea - if the charger thinks that the pack is bad, it should not charge it, period. Just a personal perspective.
Do you have a local storefront, or someone locally that's carrying your gear?