I agree broadband in the home is generally decent now in Thailand, no complaints there.
Out on the street is a different matter, and obviously depends on where you live. "True" offer an ultra wi-fi service, with speeds "up to 100 Mbps". They say "100,000" hotspots, sounds impressive, until you learn that includes all the "partner hotspots" abroad well. The actual list inside Thailand is here:
http://www.truewifi.net/ultrawifi/location_detail.htm
Its not quite 100,000 ... its actually about .... 45
As for speed, I don't live near one of those 45 locations unfortunately, but if you live in BKK you should be able to test them out pretty easily and see what the real speeds are.
Certainly 2013 will see a further explosion in mobile internet use in Thailand, what with competitive 3G (meaning reduced prices plus better nationwide coverage), plus all the new wi-fi spots.
As if Thais didn't spend enough time on facebook already