I will first start off by saying: WARNING Do NOT watch this without at least briefly reading up on what happens after the end of the regular anime series, otherwise you may risk being confused as heck. Now...I've read the manga before checking this out but I can tell you now that it's a VERY faithful adaptation of the ending of the manga. Unfortunately that does not make it very successful as a standalone OAV, story/plot wise as you need to have read at least a couple chapters back to even remotely know what's going on. In that sense, this is more of a "teaser"for what/how it could have been animated if the tv series had continued until the end....and in that respect this is sadly nothing more than granting nostalgia for manga readers and just 'flashy sequences' for everyone else.

Otherwise the art/sound/etc are on the same level as the tv series.
(The anime art style made my eyes burn so I may be biased in that regard as well)