I actually meant to start a thread about this a while back. I have played three matches on plastic this year, and I and my teammates are unequivocal in our hatred of them. 

We have had loads of injuries while playing on them, and have some players who simply won't/can't play on them. 

I am pretty injury resilient (touch wood) and have played 200+ national league games without missing one through injury. I dread to think how high the actual figure is, not to tempt fate, as the last time I missed a game through injury was c.2008 with a pulled hamstring. 

Anyway, I have suffered far more niggles and injuries which can be played with on plastic than on grass. On top of this there are the superficial injuries, and I have had pretty severe grazes to knees, elbows and my face after each of these games. On two occasions my knees have bled through my chinos in the hours post game. 

Further evidence of the injuries caused by these pitches is the sheer amount of time spent on stoppages for injury because of them. In our last game on plastic we kicked off at 3pm and didn't finish until a few minutes past 5pm. It felt like the game would never end. 

In summary - get rid of them or only have them as emergency fall backs when there has been lots of rain and games would otherwise be off. 

Trying to get an angle in this.

Is it the actual pitch or difference in how a player plays on the pitch?

Is it a lack of give, the length of the 'turf', the type of footwear worn, the watering/maintenance, the rubber crumb?

Are some better than others?

Is it different to.playing in hard ground at the beginning of the season?

Do other sports suffer in the same way? If not, why not?

1. Combination of factors, see 3. 

2. I nor anyone I have played with or against have acted differently due to playing on plastic other than obvious adaptations you might make to game style due to improved conditions for handling, kicking etc. Contact is treated in exactly the same way. The only exception has come when it comes to the act of scoring, as most choose to avoid sliding to score if at all possible. I first played on plastic in 2012 and in the past 8 years can think of one occasion where a player did not score in the corner because they modified the way they tried to ground the ball due to the surface. This isn't a factor when it comes to injuries. 

3. They are firmer than start of the season dry pitches, and have very little give in terms of players landing on them. There is also very little give in terms of traction and I personally have experienced turned ankles on a few occasions as my studs have stuck while being tackled and I have 'gone over' on the joint. I haven't experienced this on grass.
In terms of grazing, I have picked up bad grazes on dry pitches at the start/end of a season, but these have always tended to be from one big slide and usually on a hip/thigh. I don't usually pick up grazes all over my knees and elbows from them. Whereas on plastic, almost every contact creates grazing particularly to the knees and elbows, while the big grazes to hips/thighs also occur. I have concerns about the regularity with which this can happen. 

4. Yes, undoubtedly. I have played on one this year which was significantly worse than any other I've encountered, but I dislike all and have issues with even the 'best' plastic pitch. 

5. Yes, see previous answers. Also grass mitigates for a lot. There are exceptions - the surface I played on in a promotion playoff last year was ridiculously poor. 

6. Not as far as I can see, due to the totally different nature of the game. Yes footballers will graze their hips/thighs on plastic surfaces, but how often do they hit the ground? Playing in my position as a back 3 and sometime auxiliary centre, I could reasonably expect to make 15+ carries and 15+ tackles per game, plus hitting 20-30 rucks. That could result in as many as 60 contacts with the ground. It's interesting to not football moved on from plastic pitches more than 20 years ago. 

I think rugby is pretty unique in terms of the interaction between player and playing surface. The closest direct comparison would be American Football, but again the number of contacts between ground and player are low - a running back in a run heavy team might expect around 15 carries per game, resulting in perhaps 10-12 tackles, assuming they make it to the sideline on a few carries. That's a significantly lowered amount of contact with the playing surface. 

RE: 'Synthetic blend' surfaces, I've not had the pleasure but from what I have seen of them on TV, i.e. Wales home games on the Principality's Desso surface, they look to be very good but they are hugely expensive and take a lot of maintenance. 

The other problem I've heard of is that there's no give in them, so when players change direction their studs get snagged, causing injuries to knees and ankles.  I think on hard pitches the studs don't break the surface, whereas on artificial pitches there's enough depth for the studs to get purchase, but when you twist the soil would break around the studs to allow more freedom of movement.

Fewer scrums in Hockey.

Astro was better than some of the earlier sand and shale based hockey pitches. 

On worn, hard, grass pitches you would get abrasion injuries  but 3g injuries are more akin to a friction burn.

I haven't met a player yet that prefers 3G to grass

It would have to be. I still have scars and bits stuck under my skin from 40 years ago!  Seems completely wrong for rugby to me though.

Not when i played hockey 

Have seen a fair few games on Maidenheads (which is made the by the company that then laid Allianz Park i think)

Have seen Exeter & Ding's pitches and also several of the RFU AGP's 

I would say at lower levels (age grade and 2's 3's level) where players are less fit you tend to notice by 60mins fwds are "flopping" into rucks and when they do that you get knees into heads and people just not in full control of their impacts which is dangerous. At a higher level it is the pure mechanics of high speed/force impacts between skin and artificial grass causes friction which causes heat which causes burnlike grazes