pg_upgrade: What is changed?

I'm working on pg_upgrade concept. I try to determine what is changed
from 8.1 to 8.2. There is list of important areas for upgrade and
suggested action.

1) BKI - catalog.
    There are a lot of changes. See attached file.
    a) There is new table pg_shdescription
        action: create
    b) There is new record in some tables.
        action: insert
        question: Should be any OID conflict during insertion?
    c) Some records are changed
        action: ???
    d) Some record are removed
        action: keep it
        question : Is it safe to keep for example record in the pg_proc?

2) GUC - postgresql.conf
    a) New variable.
        action: nothing
    b) Some changes (default, context)
        action: nothing
    c) backslash_quote is removed
        action: removed from postgresql.conf

   There is list of GUC changes:
    ssl (assign hook)
    array_nulls   (new)
    escape_string_warning (default false->true, context
PGC_INTERNAL->PGC_USERSET)
    allow_system_table_mods (new)
    ignore_system_indexes (new)
    post_auth_delay (new)
    join_collapse_limit (description)
    backslash_quote (removed)
    search_path (default $user,public -> \"$user\",public)


3) pg_hba.conf, pg_ident.conf
    no changes


4) Disk layout is same - version 3

5) Tuples
      question: Does have data types some disk representation?
                Does have tupleheader same structure?

6) Indexes
      question: Any changes on disk representation?
           Should be possible remove all index before upgrade and recreate
them on the new version instead upgrade index structure?

7) Change PG_VERSION files

8) WAL/XLOG
     Question: Should be deleted?

9) ...

     Any other ideas?



Zdenek