There are occasions when routing to a site appears to be completely and utterly insane, and it's not always obvious which ISP is responsible.
A BGP looking glass giving skilled users the chance to interrogate the BGP tables at interesting routers in AAISP's network (the LNS, the Ethernet termination point, any other routers where customer services terminate) would enable users to check whether apparently insane routing is AAISP's fault (in which case we chase support), or another ISP's fault (in which case we chase them).
As an example; at one point, packets from you to Goscomb's UK infrastructure were routed via Amsterdam. It took quite a bit of prodding people to determine that this was because Goscomb weren't peering with you in the UK, were connected via Level 3 in Amsterdam, and were using AS prepending to ensure that Level 3 was the preferred BGP route. A looking glass like http://lg.level3.net/ would let us see that AAISP weren't the ISP preferring passage via Amsterdam, and would let us put pressure on the right ISP to fix it.