i was having problems with 2.0 and 2.1 for shrew ipsec clients where the initial connection would work fine, later subsequent connections would seem to connect but would fail to pass data
i tried disabling NAT-T and DPD as suggested elsewhere in this forum, but the ultimate fix was to setup the pfsense and shrew client per typical "road warrior" configs
e.g. http://dekapitein.vorkbaard.nl/tech-1/how-to-set-up-ipsec-tunneling-in-pfsense-2-0-release-for-road-warriors
with the EXCEPTION of setting the P1 Proposal Generation to "Unique" instead of "Default"
[that setting change is noted in the redmine link mentioned in this thread, but its in a slightly different context of multiple clients coming from the same nat network]
anyway, since making that change, i havent seen the problem where later reconnects fail, and no need to disable NAT-T and DPD
maybe that setting will work for you