I was with Eric in Turkmenistan and can back up what he says. But transit visas are relatively easy from what I've been hearing. Don't know which way you're coming from but you should allow 5 days unless you want to pay extra and you must already have a visa for the exit country, ie Uzbek or Iran. Ankara is relatively easy (I got mine there) and I've heard that Tehran or Mashad in Iran are quite good. No turkmen embassy in Syria, Azerbaijan or Georgia.
Tashkent has not given any one hassles but it can take some time.