There are a number of concerns that can all be addressed. First, is system resources because full routes will require a lot of memory for BGP allocation. So get it if you want full internet routes.
There are also issues of becoming a transit AS to providers, asymetric/symetric routing.
Make sure to do as-path filtering to prevent becoming a transit AS to your provider(s).
ip as-path access-list deny ^$
As for routing symmetry... really depends upon the design (e.g. backuplink, bandwidth, location dependent inbound/outbound routes, etc.)
The routing symetry can be controlled with local-preference for your iBGP at the BGP gateway routers and MEDs to provider or as-path prepending to the provider with your own AS number (you'll have to work on this one to make it effective). At any rate, talk with your provider and find out what their routing policies are and work with them on your requirements to ensure the routing symetry works to your requirements.\
Another thing is hard set your routes to the provider at the BGP gateway routers with a static route (e.g. ip route w.x.y.z 255.255.0.0 null 0 253). This will minimize route flapping to the loacl interface and minimize any route dampening penalties incurred as a result.
There is more, but to keep this short, I would recommend reading Internet Routing Architectures by Hilabi to get a really good feel for BGP. Then you can translate your design goals into specific requirements.
HTH
andy
