I dont think there is a whinge about it as such. Everyone knows Khaled's policy: it will be ready in due time and not a day before.
As to why people may want new versions:
1. Bug fixes. Look at BUG REPORTS forum.
2. NEW things tend to be more exciting than the OLD things
3. People see some other client bringing new features and may have similar expectations in relation to mIRC. Look at FEATURE SUGGESTION forum.
A good, working but otherwise dead products become just that: dead. Look at PIRCH.
Longevity of 6.03 can indicate either of few non exclusive things:
1. It is very stable with few bugs.
2. It is stable with many bugs taking long time to resolve.
3. There is a long list of new features on the drawing board.
4. Next version may be a total rewrite using new tools, techniques, principles and/or ideas.
5. None of the above
My personal post about "resolution 2003" was an attempt to view the anticipation with a bit of humour.