First off,  I would like to explain that I have had a lot of experience playing games in the Monkey Ball franchise and several of my opinions on the latest game might be biased because of what I was expecting.  I will try to explain why I like and dislike everything that I did in this game and why.  This way, you can form your own opinions from this piece on whether this game would be of interest to you.  

For those that are uninitiated in the series, you control a monkey in a ball by actually tilting the level and getting it to roll to a goal at the end of the level.  The control methods have changed.  On the original games on the Gamecube (SMB1&2), the world was tilted by using either the Directional Pad or analog stick.  Next, I'll act like SMB Adventure didn't exist because it was a huge departure from the series and frankly, it wasn't very good so let's not worry about the controls on that one.  Super Monkey Ball: Banana Blitz, which was released at the Wii's launch, changed up the control method by allowing you to tilt the world by using the Wii Remote.  It also introduced a jump button which fans were divided on.  The latest in the series, SMB: Step & Roll let's you use either the Wii Remote of the Balance Board.  It also has been known to have several minigames which have ranged from great to terrible over the years.

The brilliance of the series, in my opinion, is that the premise was simple and the early levels were fairly easy.  As the game went on, the levels got much harder until it got to the point where they were nearly impossible.  The bright colors and cute look of the monkeys in balls deceived you into thinking that it was going to be easy and once it got you hooked, it showed you that these games were painfully hard and took all kinds of dedication to complete.  World 10-5 on SMB:BB is the single hardest level that I have ever completed in my life and that's saying a lot.  I could write an entire thread on that one level, but I digress...

Also, on SMB:BB there were ten worlds.  In order to get world nine you had to not only complete every one of the first eight worlds, but beat every one of them without using a continue.  This would get you a crown for each world.  You also had to get a crown world nine in order to get world ten.  It took a combination of practice, dedication, patience, and skill in order to be able to do this.  It is a way of life if you will...     

Well, I'll get on to what I consider to be the pros and cons of the latest game and why.

Pros:

The graphics are the best in the series.  Everything looks extremely smooth and there are no hiccups in the framerate.

The 21 minigames are well done and all actually work unlike most of the 50 abyssmal minigames in SMB:BB.  The minigames are nearly as good as the excellent ones from SMB and SMB 2.

The music, like all of the Monkey Ball games, is phenomenal.  It is so good that it might actually be the best in the series.  The music for the Far East world is my favorite and is as good as any arcade style music that you're ever going to hear.

The characters, as always are full of personality.  Aiai, Meemee, Baby, and Gon Gon return.  They are joined by Jam, who while not a playable character might have the most personality of them all.  He is there for the tutorials and for comic relief.

The Wii Remote controls are excellent and are extremely tight. 

Marathon Mode is a welcome addition.  You can try to complete worlds 1-3, 4-6, or 1-6 all at once.

You can play the mirrors of all the levels.

They have gotten rid of the awful boss battles for the previous game (also the jump button is gone and that is good or bad depending or your preference).

Cons:

The game is way too easy for a Monkey Ball game.  The first three levels you will have difficulty dying.  To be honest, levels 4-6 aren't really that hard either.  The difficulty is more about navigating mazes or going really fast to reach the end of the level before running out of time.  In the earlier games, the later levels were ridicuolusly difficult to just stay on.

There are only seven worlds in the game and while the final level has some difficulty, it is not much of a problem for veteran Monkey Ballers.

Crowning is gone.  You get a crown on each level for just finishing them.  You can die as many times as you want doing it.  You get worlds 4-6 after beating 1-3 and world 7 for just completing the first six.

Co-op is lame.  One person controls the monkey while another shoots everything in the way.  *yawn*

More obstacles are put in your way if you are using the Wii Remote.  While this is a good idea in theory, it just puts a bunch of ugly totem poles on levels that are as wide as parking lots.  It makes things more challenging, but not challenging for a veteran of the series.  Gone are the extremely narrow paths that were once a mainstay in the series.

The Balance Board just isn't an accurate enough controller for a game like Monkey Ball.  Don't worry though, the ugly totem poles are removed and now you just have to navigate parking lots that are nearly impossible to fall off of.

The overall level design shows that the developers had the Balance Board in mind.  They are full of grooves that help keep your monkey on the right path.  Between this and just figuring out where the goals are, you should be able to complete almost all of the levels with ease.

So would I recommend this game?  Not for veterans of the series that are looking for a steep challenge.  They could finish this game easily in a day or two.  Sad but true.  The people that I would recommend this game to are people that thought Monkey Ball was too hard or maybe people that have never played the game before.  That being said, it might still it might be a little too difficult for children and casual gamers.  As much as this game got all of the bells and whistles right, it failed in appealing to old time Monkey Ball fans.  It wanted to please everyone and by doing so abandoned most people.  The sales reflect this and as much as I want this series to go on, maybe it's best that it doesn't.

I'll give it a 4/10.  The visuals, sound, and Wii Remote controls are amazing, but the gamplay is wrong in most every other respect.  If you want this type of game for the Wii and want a challenge pick up Banana Blitz, Kororinpa 2, or Mercury Meltdown Revolution from the bargain bin.     

So... we are allowed to blame Mad World?

No. Blame Wii Fit!!!

Balance Board compatibility doomed this title before it's release.

That's a shame. Kororinpa will still be the marble-rolling king of my heart it seems.

I'm really disappointed. the Monkey Ball series is going downhill.
The Gamecube titles were awesome, but the Wii versions aren't nearly as fun