The inside network is accessable only through IPsec, do I need enable ios FW?

Question

I'm building a remote site, and the only traffic in or out of their inside network is via IPsec tunnels.  There is no unecrypted access to the internet.  Should I still configure the ISR firewall?  If so , why?

Answer 1

If I get your set correctly imagined (haha)
Anyway, it really depends on you:
However, for full-tunnel setup, w/c i think you have set-up there, you can enable it for better QoS and basic site blocking as well
for split-tunnel, then configure it in your remote site.
Stateless firewall configuration in IOS really is handly, though reporting wise, its not that friendly. 
Best part of stateless firewall is it can be content based.
EX: 
class-map match-any FILTER
  match protocol http host *yahoo* 
  match protocol facebook 
  match protocol youtube
#class-map type urlfilter match-any CONTENT_DROP
  #match url category Adult-Mature-Content
There are more protocols as well, and (i think) even p2p protocol can be blocked (utorrent, bitorrent etc)
Content filtering however is a subscription license and needs to be registered/enabled
SEE: http://www.cisco.com/c/en/us/products/collateral/security/ios-content-filtering/white_paper_c89-492776.html