I haven't used the Toch-N-Flow extensively, but so far it seems very good for my purposes. Many of the models I build have tiny suspension and other parts that don't go together well with traditional glues like Testors. Touch-N-Flow allows me to concentrate the welding fluid exactly where I need it and it melts the two surfaces together. Additionally, it doesn't seem to damage bare plastic parts very much at points not intended to be welded.
A negative might be the prep time for the bonding agent, filling the bottle and then filling the applicator. It's worth the trouble; however, it takes time to set it up, use the system and then store it again if you need to only make one weld.