Neal, yes and no

I have played against Tau and the single Manta arriving is just about Ok; there is not a lot that you can do to it through OW etc, so the difference between the two mechanisms is negligible from a game balance perspective. However, I suggest that the other extreme of having an entire army able to do this would be OTT (not to mention rather lengthy) though I have not played under these circumstances.
Unlike the original Planetfall, Self-planetfall is not limited to a single activation within the game and it is this aspect that is probably the most contentious.
- Formations remain off-table until they activate, so cannot be countered by evasive manoeuvers or shooting (except OW).
- With multiple drops, the player can choose the most advantageous to play which is also a big boost as it reduces some of the timing problems associated with planetfall.
- Plotting and Scattering is not a major disadvantage; indeed with multiple drops and formations it can be turned into an advantage through having individual drop points ~15cm apart. The initial 15cm player's placement of the drop zone usually compensates for the ~7cm scatter, especially where the drop zone has to be moved to avoid enemy ZOC. This actually allows significant flexibility in where the formations / army ends up.
- Arriving in multiple activations can also reduce the 'overcrowding' issues usually associated with planetfall as formations need not necessarily be placed so carefully relative to terrain.
Jaggedtoothgrin, your comments on coherency made me re-read the rules, and you are correct that each unit in the formation would be scattered individually. This paragraph in the rules is actually a hang-over from earlier versions of the SM Drop Pod rules that simulated where each drop pod actually landed. These were superceded by the Drop Pod to speed up the game (because of the time needed to place each unit in each formation), but not actually removed from the book.
Guys, is this how others play self-planetfall?