Hi,
It depends very much on what you want to do-
i.e. what services/routing protocols/port adapters/
you intend to offer/run/use/.
Basicaly you should choose one of the latest 12.0S, 12.1E,12.2S
trains.
No recipes besides the above exist, AFIK.
The best thing to do is to choose mature release train...
....like GD at the core, and more feature rich 12.2 or 12.3
at the edge where many services are neded.
But S releases are not GD, they are ED, and that is where
the problem lies..... ;-)
Good Luck
P.S. Determing the right IOS version is quite a process...
Cisco IOS refernce guide:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_white_paper09186a008018305e.shtml
