For those unaware, the /notify feature utilizes an IRC command ISON on most servers, except those that support the new WATCH command. mIRC sends an ISON packet every 30 seconds containing all of the names in your /notify list.
I would like to see 3 changes made to /notify to make it slightly more server friendly.
1. Network specific /notify lists. Yes, I know it's a PITA to make every little feature network specific, but I'm on 6 networks and have different buddies on each one. It only adds extra bytes to my ISON pollings and extra work to my On Notify events to check which $network they logged on.
2. Reduce the number of nicks sent in an ISON packet to necessary nicks only. People that are presently in a channel with you are -obviously- online, and don't need to be checked for every 30 seconds unless they part or quit.
3. Decrease the frequency of ISON checks from 30 seconds to 60 seconds. Doing this will half the bandwidth that an idling client produces. I would personally like an option to reduce this frequency to 300 seconds (5 minutes) as it's fairly unnecessary to know (for me anyway) exactly which minute a buddy of mine has signed on. More often than not it's someone else who signed on using their nick, and they quickly sign off again or get the treatment with NickServ.
(Edit: In addition to the last suggestion, you could also make SMART ISON checks... eg, if someone parts you can check if they quit after 10 seconds (many clients /part before /quit). If someone signs off you can check again in 10 seconds if they signed on again.)
These three things, amplified by millions of clients, should reduce gigabits of bandwidth consumed monthly by the mIRC collective.

- Raccoon