I ordered one from Lancer - but I had a modified engine so I can't really comment on how it would act on a stock engine.  I did however have the stock CV carb on the modified engine for a year before I put on the Mikuni VM carb from Lancer - so I can tell you what I noticed.

The VM carb reacts just a bit faster - but the engine doesn't suddenly have a ton more power than it used to.  If your other carb was jetted correctly and working properly the power increase will not be huge.

You cannot just instantly crack the carb open from a low throttle setting....you have to roll the throttle open and allow the jets to meter the fuel properly.  If you instantly open the throttle the vacuum in the carb drops really low, and the carb may not be able to pull the fuel up through the jets, and you will get a "cough" backwards through the carb.  (That is the purpose of the vacuum operated slide in the stock CV carb....it prevents the vacuum in the venturi from dropping too low when you change the throttle setting too quickly).

I noticed that it was just a bit harder to hold a steady cruising speed - a little bit of throttle change made a larger change in speed than would happen with the stock carb.  Part of this might have been that I also changed the handlebar throttle control and it may have been a bit faster ratio.

The VM carb also doesn't have the TEV valve that the CV carb did - so if you let the throttle close completely as you shift gears...you will get a louder "pop" out the exhaust.  The shifts are far more graceful if you roll the throttle off and leave about 1/8 throttle while you change gears, and you might get a bit of a grumble...but no "POW".  After a bit of riding with the new carb you will get used to it and learn how to ride gracefully.

The same thing occurs when you roll off the throttle and are using compression braking.  If you allow the throttle to close completely as you are slowing down...the engine will bang and pop and make a lot of noise.  If instead you just roll the throttle open a little bit, the noise will be reduced.  As you slowly open the throttle you will hear the reduction of noise, then if you continue to open the throttle you will feel the point at which the bike begins to accelerate....and you want to be just below that point.  You will have enough throttle to cut back on the noise - but not so much that you are allowing the engine to make power  and accelerate the bike while you are trying to slow down.  As the engine rpm decreases you will gradually be able to roll off more throttle and eventually the throttle can be closed completely.  You will have to learn how to apply the front brake with you fingers while still rolling back the throttle grip a tad.  With this carb you have the ability to make a lot of noise, make a little bit of a grumble....or ride smoothly, and it is how you use the throttle that makes the difference.

If you are cruising along at a relatively fast pace, and you suddenly need to stop in a hurry and you chop the throttle fast, grab the brakes hard, pull in the clutch instantly.....the engine goes waaaay lean as a result of the instantly closed throttle - and the engine most likely will stall.  There is nothing you can do about it - the primitive nature of the carb just cannot provide enough fuel through the idle circuit to keep the engine running when you instantly close the throttle.  

The VM carb requires you to be more of a "rider" than the stock carb, and you have to adjust your riding style a bit.  I really don't know if the bike became faster with this carb switch - it has become a bit more responsive and does require you to be more aware of what you are doing with the throttle.  I like the way my bike rides with it - but it is not fuel injection and you have to avoid just cracking the throttle wide open instantly or closing it completely when shifting or compression braking.