I will say that on the announcement about the release of 3.4.8, IPS announce discontinuing support for the 3.3.x series on January 1st, 2016. 3.4.x will no longer be supported in 2017.
I know I don't post around here a lot, but I will say that 4.0 does come packed with its own issues, however I will say that from the people that I know that use it, they say it's faster, code wise it's nicer to work with, and it is way more responsive. Go for it.