We've just been touring Central Asia. EU-passports and a 20-years old TLC.

Iran
The only hassle we had is the number plate, we entered Iran from Armenia but the police in Tabriz had run out of transit plates so we ended up with ordinary iranian plates after two terrible days at the big Traffic Police Complex next to the new TV-tower in Teheran.
Leaving Iran, we just removed our plates and keep them as souvenir.
Diesel is still cheap, about $0.02 / litre.
Roads are very good, traffic... hm interesting. Drive carefully!
Carnet requested.

Turkmenistan
We got a three days transit visa for $31 in Teheran. It took seven days to get the approval from Ashgabat but then we got it in a couple of hours.
At the border we paid about $100 for the car (road tax, fuel tax and assurance) and $20 each person. We got a transit document that stated the exact route to take thru the country.
Leaving Turkmenistan at Turkmenabat we had to pay about $10 but got receipts, maybe for the bridge, I don't really know.
About 20 road blocks but no bribing.
No carnet.

Uzbekistan
They used the carnet (maybe just because I had it) but no fees. I did't pay the road tax ($20), and didn't have any problems because of that but probably it's a good idea to pay it.
Roads OK.

Tajikistan
I got the visa (with a LOI) on the spot in Tashkent.
Big problems at the border at Penjikent. I ended up paying $90 for some sort of road tax. Got a receipt but I think that the custom officer got a new mobile phone since then.
Small fee for disinfication of the car.
Thanks to some contacts, we where allowed to use the new tunnel between Khojand and Dushanbe. The pass was closed.
In Dushanbe GAI is everywhere.
It's illegal to:
-Have a dirty car.
-Use sun protection film on the car windows.
-Don't stop at a zebra crossing (even if there is no one to cross).
-Drive to fast (even if you drive at 30 on a 40 street)
Anyway I didn't pay anything.
There are two roads to Khorog. The eastern one is the easiest but the pass was closed. The other is very fine down to Kuylab, then its get bad. Partly very bad (you need a 4WD with high clearance). There are a new strech following the river Panj.
Pamir Higway is great and open. Some snow, some pot holes but not that bad.
No Carnet.

Kirgizstan
Got visa on the spot in Dushanbe, no LOI, $40, embassy next to the Indian embassy.
At the border they just checked the passports. I couldn't get a stamp. That caused some questions when leaving the country, but no problems.
Very bad roads up to Osh. Then very good roads up to Bishkek. The last pass before Bishkek was open but demanding and dangerous. Check situation before take off.
No Carnet.

Kazakhstan
Visa took two days in Bishkek (note that the embassy got a new location), $35. No problems at the border. Cheap diesel.
Road from Bishkek to Alma-Aty is very good, then OK. No problems at the border north of Semipalatinsk.
No Carnet.

Tobbe and Reje
now in Sibiria