Aside from latency, i also hear claim that node run by mining pool connected to other node which belong to different mining pool and node run by major company. Anyway, i agree the biggest reason to use them is we don't have to setup and maintain stuff.
I don't think the nodes connected to other nodes is any different to any other machine connecting to a server elsewhere on the net, it still has to traverse the same gateways, routers, switches and other network infrastructure.
Bitcoind looks like it handles all of the node to node connections automatically anyway. In that respect it looks no different from any other DNS lookup or TCP/IP communication.
Presently I just can't see anything to support the claim that mining solo to a pool is any better than mining directly to bitcoind beyond the fact that someone else has taken the time to set-up and maintain the pool and all the backend side of it reducing the initial technical hassles.
Once I have a couple more mining boards built, I'll point them at my bitcoind server and let them run indefinately, if by chance (and it is a remote chance) they hit a block I'll celebrate that here!
Cheers
G.