Flat rate to the airport for UberX has gone down to 300B now.
I've just had two weeks over songkran there and used a mix of taxis and UberX; my very first time using the latter anywhere.
Every Taxi we had used the meter, one guy drove a bit like a maniac, but most were exactly what you want a taxi to be: use meter, drive sensible and a normal route.
Tried getting a taxi from Huai Khwang back to Suk 26 one night around 10:30pm but 3 refused so thats when I used Uber for the first time and worked a treat.
A couple of days later, we used it again to go Ban Phe Pier for Ko Samet and I think the cost (1,600B inc. tolls) was less than a taxi even on meter and 1.2x surge (a schoolboy error but there was an UberX basically right outside the hotel when we were ready to go). Its a shame on the way back had to fork out 2,500B for a "taxi" from Nuanthip pier to Bangkok (didn't fancy a bus).