For some, ADSL2+ has not produced an improvement, for others (including myself) it's significantly better. It all depends on your line characteristics, not just attenuation, but susceptibility to noise. If you have an NTE5 master socket, I would suggest trying the router in the test socket behind the faceplate - ADSL2+ is much more sensitive to noise than ADSL Max, and this will rule out any internal wiring issues. If nothing changes at the test socket, run Routerstats for at least 24 hours and see how the noise margin is fluctuating.
If all else fails, you can be modulated back to ADSL Max and retain the bandwidth allowance for ADSL2+.