I upgraded one server so far (with yum upgrade) and it seems to be ok. But i did see some smbd errors showing up in "messages":
Jan 3 21:23:11 office smbd[8107]: [2008/01/03 21:23:11, 0] lib/util_sock.c:read
_data(534)
Jan 3 21:23:11 office smbd[8107]: read_data: read failure for 4 bytes to clie
nt 192.168.171.50. Error = No route to host
Jan 3 21:23:11 office smbd[8107]: [2008/01/03 21:23:11, 0] lib/util_sock.c:writ
e_data(562)
Jan 3 21:23:11 office smbd[8107]: write_data: write failure in writing to cli
ent 192.168.171.50. Error Broken pipe
Jan 3 21:23:11 office smbd[8107]: [2008/01/03 21:23:11, 0] lib/util_sock.c:send
_smb(769)
Jan 3 21:23:11 office smbd[8107]: Error writing 75 bytes to client. -1. (Brok
en pipe)
I haven't seen the error "broken pipe" and "no route to host" in 7.2