My experience with Sri Lankan as a One World Emerald was DIRE. I have flown with them a few times and the last two have been bad. The following is an extract from the complaint letter I sent to them afterwards (to save me a LOT of typing!):

Firstly, I would like to point out that the information system in Bangkok airport did not appear to be working in relation this flight. It was saying “OPEN” all the time, it never said BOARDING or FINAL CALL – only ever OPEN. I first arrived at the gate circa 12:40pm - which was supposedly after the boarding time of 12:35pm – and the plane was not even there! There was no indication of this on the boards. I asked when we were boarding and was told to go to the lounge and I would be informed there. I (eventually) found the lounge – after having some difficulty because I checked in online and did not have a lounge invitation. This is completely avoidable – Cathay Pacific, for example, includes a lounge invitation along with a mobile boarding pass if you check in on-line. I recommend you do something similar.
I sat in front of the information board in the lounge and was informed some time later by the lounge staff that the flight “had started boarding”. The information board still said OPEN. I went to the gate and discovered everyone else was already on board – which is frustrating because I don’t like being late and again, this was entirely avoidable. Going through the gate, instead of using the mobile boarding pass, another one (paper) was printed out. Thus completely removing the environmental benefits of using an electronic boarding pass. Again, very frustrating.
Finally, I boarded the plane and found that my seat (1K) did not have any storage for small items. None AT ALL. However, since the cabin was half empty, I asked if I could move to the opposite side seat (1G) which did have room for small items under the footrest. I sat down and started to unwind after the horrible experience in the airport.
The in-flight services Manager (Anil) came to ask if everything was OK. I replied that it was now as I had moved seats and now had somewhere to put my handbag. He replied that my seat was identical to the other seat. I pointed out that it was not and suggested he take a look at the other seat so he could see for himself. At this point Anil became most agitated and said he didn’t have to look because the seats are identical. I did not realise at this point how mentally unstable this man was, so I repeated my point. He got even more upset and then started called in the ground staff and tried to get me off-loaded. At this point I realised I was dealing with someone either mentally unstable or just utterly unable to cope with his job and decided to give up explaining what was going on. I believe the ground staff managed to calm him down because nothing else happened and the flight got underway.
I did feel upset at the announcement (by Anil) that we were going to experience Sri Lankan hospitality, because my welcome was anything but hospitable. Luckily the ladies on the crew were lovely and made up for her bosses rudeness. However I feel very sorry for them having to work with such a nasty individual.
The storage in the two seats is shown in the two photos below. They are clearly different.

Figure 1: 1G - with room for my bag under the foot-rest


Figure 2: Seat 1K with no room under the foot-rest

(sorry it looks like my photos cannot be copied across)