In an ISP point of view, I think that the possibility to execute scripts up on connection or desconnection of ppp interfaces (pptp and pppoe), like if-up and if-down scripts in mainstreams linux distros, would be great.
Also, I miss very much some features that we can find in squid: tcp_outgoing_address, tcp_outgoing_tos, TPROXY and ZPH support (last 2 need patching the kernel).
If RouterOS had those features, my network would be 100% Mikrotik.
P.S.: For those not used to squid: tcp_outgoing_address allows one to define the origin IP that squid will request to servers based on some rules/acls (mime types, client/src address…); with tcp_outgoing_tos, one can define the tos bits of requests based on client/src address, file types and others…than you can do QOS based on theses rules; TPROXY is a patch to squid and linux kernel that allows squid to spoof/bind to the client’s original IP address, passing it on to the destination web server (full transparency); ZPH is a patch to squid that allows to configure predefined TOS bits to HIT packets (files served from cache), so one can bypass bandwidth control rules if objects are cached (AKA “cache pass”).
EDIT: Does anyone agree?