One common anti-pattern I notice among users who aren't fussy version 
control nerds is to resist the interactive UI.  They just want a magical 
commit-everything and will very quickly learn about record --all because 
it does what they want.

I wonder if there's anything we can learn from this?

One thing is that if a not-super-savvy user sees something like 3000 
changes, with darcs potentially offering to step through each one-by-
one, said user would be inclined to extend their middle finger to Darcs.  

Is there anything we can do that would be nicer in such case?

Would it help to have something like
“HINT: hit 'f' if you want to record all 600 changes to this file”
which triggers when there are eg. more than 10 changes in that file?

I think the idea of providing hints for such cases is good. However, you 
may end irritating the user who is already familiar with Darcs. This 
issue reminds me the question about 'darcs send' not being properly 
configured. If I recall correctly Darcs now warns you about that when 
you use 'darcs send'.

Darcs may have some "special mode" for the new user that gives such 
hints, and the option of disabling them, as many applications have.

One design option:  

When darcs record is run, it would check to see if the "suppress record 
tips" file exists somewhere under _darcs.

If not, a more verbose intro with tips is provided. 

Like some programs do, you could offer the user some options after 
displaying the tips:
"Would you like see these tips again next time you run 'darcs record'" ?

If they say "no", update the "suppress record tips" file, and they get 
the current behavior.

One question is whether you are OK with existing users seeing the tips 
once, or if you want to make sure that only new users see it.

As spec'ed above, existing users would see it once as well. They might 
not need the tips, but seeing a tip once after after upgrade is 
minimally annoying. 

If you wanted to keep open the the possibility of having tips for every 
command, you might use a single "tips" file, with boolean values for 
each command. 

I think I would personally appreciate this commands I used less 
frequently or new commands, like "optimize" or "rebase".

There are two different use-cases here:

1. The "first run" case, where extended detail on the common options is 
helpful.
2. The ongoing case, where randomly selected tips for more obscure flags 
would be interesting. 

For the latter, you could have an option to "show all tips for darcs 
record?" This could function as a form of extended online help. 

The tips system might also do some deep linking to further docs in the 
manual or wiki.

I think it is worth taking a look to the Mercurial's crecord extension 
for some inspiration. This extension is presented in this video: 
http://vimeo.com/13353810

Mmm, UI speculation stuff.  Hopefully a needs-diagnosis/design status 
and UI tag will be useful for somebody trawling through the BTS later 
to see things we can look at.

If anybody wants to work on this more, don't forget you can use 
http://darcs.net/Ideas/ as a place to flesh out more detailed ideas for 
UIs/subsystems