What I liked most...
21. Added /play [-a] [alias] [channel/nick/stop] <filename> [delay]
43. Extended $disk(path|N)
45. Added identifier warning option to editor dialog options menu, halts script if identifier doesn't exist.
61. Added $msfile(dir,title,oktext) identifier, same as $sfile() but allows selection of multiple files.
68. Added custom file-handling commands and identifiers, which allow you to open multiple files for reading and writing.
72. Added $rawmsg, returns raw server line for server events.
143. Binary variables no longer have an upper limit on the number of bytes that can be stored.
144. Added $compress(file|&bvar, blN) and $decompress(file|&bvar, blN)
165. Fixed /did not showing/hiding tabs and their contents properly.
166. Added $comcall(name, alias,...) and $dllcall(filename, alias,...)

Things I disliked the most...
23. /dcc commands, such as /dcc send, ignore, etc. are now also handled in the form /dccsend, /dccignore, etc.
- Why?

Things missing that I really wanted to see....
- Tree-like structure for the switchbar
- enhanced dialogs
- a pre-exit event that occurs before all disconnects and the final exit event
- on :MIRCERROR: event (also stated by someone else)
- Still not properly reading file sizes (with $file().size) over 4GB on NTFS partitions.