I've been having complaints about the Grand Prix's at Mario Kart Wii as well!... In the 150CC (And even a little in the 100CC) it's also a matter of luck which decides the outcome of a race! You can race as good as you want, everytime that i'm standing in 1st place for like 2-2.5 laps... I get hit with for example; a blue shell, a red shell, and then someone nocks me to the side, thus loosing like ~10 seconds and ending in 8th place... I'm trying to get a 2-star ranking in all grand prix levels but this annoying AI is really making it hard to get such a ranking in the higher CC-classes, however not impossible! It really doesn't come down to racing skills for your ranking, i believe my racing-skills are 'good enough' for a star ranking, only if you get hit on the wrong times by really overpowered stuff multiple times, i really can't help it... And then the game gives me a (for example) A or B rankings, bullcrap if you ask me! And that is what i REALLY HATE about Mario Kart Wii! This was, to a lesser extend, also in Mario Kart Double Dash!! However, the DS-version had a much 'fairer' AI.

Time Trials and online rankings, downloading ghosts from friends and trying to best eachother on tracks makes more then up for that though!

 In many tracks I can lap the computer opponents in Mario Kart Wii too (in 50cc) and some tracks at 100cc. but they are too fast in 150cc, the nearest I can get is in Ghost Valley because they don't take the shortcut.

@tuoyo. It is an annoyance sometimes but it would be really boring if I won all the time.

getting item raped at the wrong time in an online race is actually more common than in 1 player GP mode simply because people are more intelligent, which means if second place sees a blue shell passing he/she knows that is the right time to send a red shell (should they have one) because 1st place will be unprotected after the blue shell, same for the POW block.

I agree with most of that save for blue shell not being enough to lose.  I had a race yesterday where I was better than all the other players and on my best track but finished 8th just cause of the blue shell.  First a blue shell, then I lose my items, then I get hit by a red shell, then I get crushed by a giant racer.  All after leading the race from start to the very end.  On another race I was in 1st place with someone chasing me down throughout.  Then on last lap I get hit by a blue shell, he overtakes and wins.   

But I agree most of the time if you are better than your opponents you will win but sometimes luck would come into it.  I also agree that is what makes Mario Kart so much fun.  That was the difference between the multiplayer quality of MK64 an Diddy Kong racing.  In Diddy Kong you would find yourself racing all by yourself cause you are so much better.  It gets lonely and boring.  In Mario Kart on the other hand you would have to be on your toes right till you cross the line.  What I have a problem with is the blue shell.  I think it's too random to punish just the person in 1st.  Why not 2nd?   Lightening, POW I am fine with as affects the others.  But the blue shell has no justification whatsoever.  Unless it was only possible for it to appear if 1st was miles ahead of the others.  But that is not the case.

Don't play on hard. Problem solved.

If you guys are really annoyed with blue shells, there is a glitch you can abuse to get rid of them. I haven't done this online, as I've seen people been week-banned, and I don't want that.

What you do, is that when you hear the Wiimote speaker yell, you start sliding until you hit a 20-50 degree sideways slope. Right before you hit it, you wheelie. This causes you to change your driving degree, and makes you head a bit more to the left that you otherwise would have. For some reason, the blue shell cannot find you now, and turns back and hits the second place.

This doesn't work on all courses, and not everywhere, but it is helpful if you don't mind semi-cheating. I have only done this a few times, as I feel it is more than semi, and I haven't checked it out in TT or WFC

Ok, another shortcut you can do on many courses. If you have Bullet Bill and jump off the course, straight in direction of another platform, he takes you there if your nose is headed there. I wouldn't count this as a glitch, but some people would.

To avoid a pow-block, start sliding, hit a 20-50 degree sideways slope, release the slide button, and start a wheelie. If you timed it right, which is fairly easy, you won't get hit at all. I don't count this as a glitch either.

It's clear that one Blue shell won't make you lose a race, it's just that three of them do.

 If you read the instructions, POW shakes the ground.  It doesn't affect you in mid-air

 I'm completely with you there.  I don't understand all the complaints about the rubber band AI.  I haven't seen it myself.

 Have you every noticed that when you're in 12th place you get all these insane power ups that totally screw the people in first place?  

Yeah, it doesn't sound so bad when you realize you get those same powerups when you're in the lower places too. 

Actually that doesn't really happen much. The powerups you get when you're last rarely affect the person in the first place. As far as I remember, you don't get the blue shell in 12th place. There's the thunder cloud, but that affects everyone almost equally (the slight difference is in the timespan of being small, which I believe is bigger the better your position is).