+++Warning, this will contain some spoilerish material from previous seasons, but no major giveaways from season 5. If you have not seen the prior seasons proceed at your own risk. +++
Chances are, by now everyone knows what the show is. In some ways it has a similar feel to what is has since it found its footing as a show. In other ways this season was different. It still kept the case-of-the week, intertwined with larger story lines. Chin got one of the larger arcs after having found out who killed his father last season, his father's killer becomes an increasing foil throughout the season. Danny got a couple larger arcs over the season, one expanding the story around his brother who we last saw escaping in a plane, and the other involving Rachel working her way back into his life.
I think the one thing the show is suffering from now is having too large an ensemble cast. With the addition of Chi McBride and Jorge Garcia as series regulars, there is just not enough for everyone to do. As a result we see the team split much more, sometimes with a couple members working on an different part of the case (or a totally different case) or some characters totally absent in a given episode. The stand out episode, to me, of the season was the 100th episode which re-told the events of the pilot episode if things had turned out differently, and culminated in another Steve vs Wo-Fat showdown. This season also saw the return of Terry O'Quinn as Joe White for a few episodes and Michelle Borth as Catherine in the season finale. The season finale also set up what is likely to be the main arc of Season 6.
For those who get the discs, obviously as the title implies the lack of blu ray sucks. This is one of the shows going the cheap route and only releasing it on DVD. While the picture and sound are okay, those who get the discs are robbed of the HD experience we got the first few seasons. Extras are similar to what they have been before. Deleted scenes on many episodes. Limited commentary tracks (I think only 1 or 2 episodes had one this year) and then on the final disc a few behind the scenes features and a gag reel. There is also a feature on Daniel Dae Kim's directorial debut. Good for what is there.
All in all, the season is good. I wraps up some story lines, and sets up others. The action on the series continues to be top notch and the stories are still engaging. If you can live with the lack of blu ray the DVDs are worth getting, but if that is a deal breaker or you do not care about the extras then streaming it is probably the way to go.