Hi @omarfilip,
I have completed my import from IPB recently with help of @pfaffman
I found, however, using rake commands to slow for fixing quotes and stuff as my forum has 1.3 mln posts it does take time.
I prefer to do all of the stuff directly on the database and then to rebake.
For the quotes for instance I would do:
UPDATE posts SET raw = REPLACE(raw, '[quote=', ''||chr(10)||'[quote=') where raw like '%[quote=%';
UPDATE posts SET raw = REPLACE(raw, '[/quote]', '[/quote]'||chr(10)||'') where raw like '%[/quote]%';
and then rebake.
I would actually fix everything I can before I even start rebake as you can see you changes live by simple regenerating HTML or editing the posts.
Hope it helps!