As a format, the opportunities offered by CD to add large amounts of music to a collection with relatively affordable outlay are currently fantastic. The 'Original Album Series' 5CD sets are a great way to plug gaps, many artists' albums are being collected into attractive boxes (Springsteen, Todd Rundgren, Cars, Roxy Music etc. have all had nice sets recently), and in the classical and jazz arenas there have been some fabulous big boxes (DG111, Decca Sound, Columbia Jazz, Berlin Phil, Vienna Phil, Glenn Gould Remastered, Brendel Complete Philips Recordings etc. etc.). Stuff that has been unavailable for years has also been reissued, including some of the discs in those big classical sets, and also material like the output from the band The Long Ryders, recently issued in a nicely executed set by Cherry Red.
There have also been some very nice reissues of older albums with additional content. For example, the on-going series of Jethro Tull hardbook reissues is excellent, and I'm looking forward very much to deluxe reissues of some of the classic Barclay James Harvest albums (Everyone Is Everybody Else and Gone To Earth are both due out on Esoteric in June, including new remasters of the original album, and new remixes from the master tapes). A particularly good reissue in recent years was the deluxe edition of 'Tales Of Mystery & Imagination' by Alan Parsons Project, which included both the original album mix, and the later version with the added guitar parts. Even albums like T'Pau's 'Bridge Of Spies' have had very good extended reissues.