lagg is ultimately a problem as a high-availability solution since most switches do not support multi-switch 802.3ad yet, and most probably never well. So you are limited to a single switch. So 802.3ad is good only for aggregation, and not for high availability.
What about using STP or RSTP instead of lagg? Which L2 managed switches
like 3com and HP support. Then you could connect each of two NICs to a
different switch, as well as connect the switches to each other.