Best described as patchy.
Free wifi is available in some hotels and campsites plus in many restaurants. McDonald's deserves an honourable mention for almost always having free wifi.
There is still a surprising number of establishments charging a silly amount for an internet connection (€6 per hour / €20 per day being examples).
Connecting to the net via mobile phone data roaming is still outrageously expensive. This may be more to do with my home carrier than the French carrier but they wanted to charge me 1c per kb. No thanks. The EU has tried to clamp down on excessive mobile phone roaming charges but you can still clock up a €50 bill browsing a handful of web pages before your phone company has to notify you.
One very positive and yet frustrating thing was the widespread availability of mobile internet signals both Wifi and 3G in almost every urban area of France. I get the impression that just as in Ireland mobile access through the 3G network is becoming the internet mode of choice for many people. Unfortunately all of these seem to be locked behind long term contracts and it doesn't seem to be possible to sign up for shorter periods like a day or a week. Given the huge volume of tourists in a region like Paris I am surprised one of the mobile web companies doesn't offer a pay by the week package. Something like €10 per week for 3G or Wifi Hotspot usage would be reasonable.