PixlBit

And I like it!

I held off from buying MK8 for a few weeks, but finally caved and bought it on a very boring day.  If I knew more people who planned on buying it, I would have bought it on day one, but alas, I know none, which sucks, because I'm all about playing multiplayer.  Simply put, I hate gaming alone.  On top of that, the Mario Kart Wii experience was fantastic.  Many friends also had it, and on any given night there'd be 6-10 of us playing simultaneously online, which was a blast.  I would go as far as saying that MKWii was the best online multiplayer experience of my life.  I guess what I'm trying to say here is that MK8 is a better game, but MKWii, so far, was a better overall experience, which isn't the game's fault by any means.  Here's a breakdown of some of the newness:

Visuals

The HD visuals are superb, and, quite frankly, long overdue.  What more can I say?  It looks great.

Bike/Kart Balancing

My major pet peeve of MKWii was the bikes.  They seemed to have a slight speed advantage, as evidenced by racing against top-ranked ghost data, and other skilled racers online.  Wheelie, wheelie, wheelie... 'Nuff said.  Thankfully, that advantage appears to be neutralized... APPEARS to be.  I haven't put enough time in to really tell for sure.  I don't enjoy racing on a bike.  It's Mario Kart, dammit, not Mario Bike.  The steering of the bikes never felt right to me, so I stuck with the karts, and am glad I can do so this time around without feeling at a disadvantage, if ever so slight.

Anti-Gravity

To me, the anti-gravity aspect is mostly superficial.  The vehicles behave the same as they would with wheels on the ground.  While the player may in fact be racing upside-down, the farthest the camera angle will rotate is to the side, which is good, because racing upside-down would be pretty tough.  As long as you are focused on the track, you never actually feel upside down.  That is unless the focus of your gaze wanders to the background.  In that case, it will mess with your head a little bit.

While in anti-gravity mode, players may activate a boost by bumping into another racer.  This can also be done by bumping into "bumpers" located on the track.  For the most part, I avoid the bumpers.  They're never located on the tightest racing line, and steering away to hit one usually sends me off the track or out of control.  Considering this, anti-gravity doesn't add much in terms of execution.

Online Play

Online matchmaking is similar to that of MKWii, with a few tweaks.  A player's rank begins at 1000, not 5000.  This may create a perception of a level playing field.  A beginner at 1000 rank entering a lobby against someone with a rank of 3000 may feel less intimidated than against one of 9000, although 3000 is probably equivalent to 9000 in terms of skill.  Also, this might help add replay value, as achieving 9000 will take considerably more time starting at 1000 than at 5000.

Selecting which course to race is also different.  Instead of having all 32 courses to choose from, only a pre-selected 3 are available, with the 4th selection being a random selection of those 3.  This helps prevent racing the same track back to back, or the opportunity for a player who is skilled at one course from selecting that same course repeatedly.  

Another added feature is tournaments.  While not entirely new (MK7 on 3DS had 'em), it's a departure from the regularly ranked races, can be modified to allow certain items and other variables, and is still fairly competitive.  It also has its own unique ranking, so players who are serious about their public rank have an alternate competitive option to play when they want without affecting their standard 1000+ rank.

Worth mentioning, but not a big deal, are the chat bubbles.  Chat bubbles were available in MKWii only in arranged matches.  Now in MK8 they can be used in public matches.  Still no voice chat, though.

Other Subtle Changes I Noticed

-The frequency of Blue Shells has diminished greatly.  I'm hard-pressed to remember a race when I saw one more than once.  I will say, though, that they always seem to be launched during the second lap...  while I'm in first place...  and 2nd place is right behind me...   Grrr...   Also, Blue Shells travel along the ground in MK8, like in previous MK's, but not in MKWii, which saw them travel through the sky.  

-Item boxes seem to regenerate faster than in MKWii, which I like.  

-Falling off the track is now more forgiving.  Cloud-riding Lakitu swoops down fairly quickly, grabs you, and usually drops you ahead of where you fell off the track.

-About Blue Shells - they no longer force the player to drop the item they were holding when struck.

-Even more about Blue Shells - they can be destroyed using the Super Horn!  Finally, a bona fide method for defending against the dreaded Blue Shell.

-While dragging an item, a player connot receive another item by collecting an item block.  I personally don't like this feature.

Overall

There's a lot more I could say about the game - new items, new characters, new courses, etc - but I'm not here to give a full rundown of the game.  For that, check out this site.  There's nothing I would call "revolutionary" about MK8, and that's fine.  It's an already excellent franchise that shows incremental improvement with each release, and rightfully so, MK8 is now the best.  Players of MKWii should be able to seemlessly transition to MK8.