For anyone who doesn't already own the previous Blu-ray release of this trilogy, then now is the time to buy - But there's a caveat.
But first, the quality of the films:
Mission Impossible is a very well crafted film. It has action, appropriately placed jokes to break the tension once in a while, and believe me, this film does a great job at keeping the tension palpable, and the acting is great all around. It actually even adhered to the original series method of storytelling to a certain degree. Top notch film for anyone who's a fan of suspense and action.
Mission Impossible II... meh. I enjoyed it for what it was, a mindless popcorn action flick. Directed by John Woo (Broken Arrow/Face-Off), the M:I formula is thrown out of the window, the character of Ethan Hunt is transformed into a cocky arrogant, and the only thing remaining is lots and lots of action, which has a tendency to be a little hard to swallow at times. That being said, it's still fun to watch. This is pure action eye-candy, and if you're OK with that, you're going to have a lot of fun. If not, well...
...The Mission Impossible III at least comes in to save the franchise. Directed by JJ Abrams (Alias, LOST, Star Trek), this film is a true return to form. A great story that's paced out evenly and some mindblowing action. Personally, it's still a shade under the original, but this film holds its own very well.
The best thing about all three films is that they're all seperate entities for the most part, meaning, you don't have to see any film before you see the other.
Now, back to that 'caveat' I was talking about - The audio. It's all LOSSY audio, which is fairly inexcusable for a Blu-ray in this day and age. Yes, it's true that this boxed set has the same exact encodes in video and audio the original releases had, and that was pretty early in the HD game, but that's STILL no excuse. The studio really should have just taken the lossless audio and made a new encode for this release. So, what now? Does the studio give us 'proper' releases after the fourth film hits Blu-ray? My personal opinion is this - If they release a four film boxed set at that time, you're not going to get anything new from the original trilogy. So you may as well pick this up now. After all, the price is pretty stellar.