In Cali, we've had them for MANY, MANY years.  It's a requirement in the city of Los Angeles that you have to have the low flow shower heads and toilets (they even have an inspector come out to specifically check for that).

You can't even buy the 4 gallon flushers anymore.  Now they're the dual flush ones with a button for liquid waste only (half gallon flush) and one for solid (the full gallon flush).

Hasn't been an issue here.  Just have to flush twice (or more) sometimes...

I remodeled my master bathroom and got one, no problem.

As Ryan mentioned, in most  SoCal counties, it is a retrofit requirement: low-flash toilets and shower heads. 

I have installed several of these in my rentals with short lines to the sewer system...I will not do them on long runs...I had a septic pumper warn me of that

Have not encountered issues; they do save quite a bit of water, especially compared to much older models. I actually wrote a post on the subject some time ago; here's the link: http://actvra.in/4sWW

I've not experience any issues, but I've not lived with one either.

I have not had experience with them.

More problems than they're worth. I'm sure the plumbers love them though.

I've seen some where there's too little water.  The better ones have a second larger flush option that seems to work.

They seem to work fine for me.

They work. More flushes may be required.

All the ones i've seen have worked well. I actually saw a waterless urinal the other day.

I've not heard of or experienced any issues.  We have a lot of them in CA ... which has been in a state of drought for many years. 

They have all been fine. I've personally had a few (& probably used a few). One of my listings has a fancy Japanese toilet that costs $700. I guess it blow drys, fluff's (lol) & the seat is kept warm. 

I'm personally afraid of the thing.

I have a new toilet and you hold down the knob different times for different types of flushes.  A quick push for light volume, a longer push for heavier volumes.

I think it all depends on the brand. Some just are not as efficient as others... 

I hadn't heard of any problems but now that you mention it I wonder.  

We can thank ALGORE for these! Along with the amazing Internet he founded! Most of these have plungers sitting next to them.

My stepson as this type in half bath, no problems.

Sally K. & David L. Hanson I have one where it has two buttone. One with one drop of water and one with two drops of water. I'll let you guess what the drops mean. No problem with either one.

Too little water sometimes doesn't move the waste and one has to wonder if anything in the pipeline gets stuck down the way because of little flow too

I think the newer ones are far better than the original, hwever i do notice you get what you pay for, so the $69 dollar builder basic model toilet will not have the flushing power of a good one.

Nope, never had a problem here in California where they are all over. In Hawaii, I saw a lot of Toto toilets in luxury condominiums. People swear by them.

No

Benn in CA for years. AND REQUIRED. They have single and 2 stage styles. The single wastes more water 'cause often folks say you gotta flush twice.