Comfortable sqlplus interface?
but for example no "arrow-up" key for the previous history entry is available.


You're talking about sqlplusw the "GUI" tool - the oldschool sqlplus does support 
arrow-up-bring-previous-statements feature.


  What is a good replacement / extension for sqlplus


Oracle's SQL Developer, a free GUI-based tool, is pretty neat. 

If you're a vim addict, there's VoraX which is augments SQL*Plus very well.


  VoraX aims to be a simple, yet a powerful IDE for Oracle databases. Instead of reinventing the wheel, VoraX relies on the well-known SqlPLUS which is actually used to connect to the database, to execute SQL statements and to get the results back. However, this interaction is hidden from the user who just uses his/her Vim environment without knowing that, behind, a SqlPLUS process does all the work.
  
  The big advantage of this approach is that almost all SqlPLUS commands may be used without a problem. You can format columns, set pagination, autotrace queries etc.
  
  FEATURES
  
  
  99.9% of the sqlplus commands supported
  advanced code completion
  it runs on Windows and UNIX
  a nice results window with highlighting for errors and logging support
  a database explorer which may be used to browse the database objects in a hierarchical way
  support for editing and compiling PLSQL objects like packages, types etc.
  convenient key mappings for: describe object under cursor, execute current statement etc.
  connection profiles management (including securely storing of passwords)
  fuzzy search for database items
  offline search for Oracle html documentation