My parents presently work in Sri Lanka (I study in the UK in the meantime.) I've flown twice with them; once London-Colombo return and once Colombo-Male return.
If I was being honest with you, I'd have to say I was not overly impressed with UL service. The cabin attendants were fine, however, the flight was delayed from BOTH ends (Heathrow and Banderenaike) by 1 hour (Heathrow) and 3 HOURS (!) at CMB. What made the delay particularly annoying was the fact that there was no explanation for the delay!
Before EK took over, there were many stories among the expat community in Colombo about UL's notorious "Delayed" or "Cancelled" flights. Most expats (those are english/american etc. living and working in a foreign country) avoided the airline completely and flew any other airline (Emirates/Gulf Air/Singapore Airlines etc.)
However, I haven't flown since EK started taking over; despite the above, if you have the choice DO FLY with Air Lanka. A new airline is a new experience; you'll be able to form your own opinion, and get the chance to try out an A340 (if you haven't already done so).
GO FOR IT!! Ayubowan Sir. ("Welcome" in Sinhala).