1 year on, and I still haven't come across a single good Hainanese chicken rice spot in KL, in fact *any* which can hold a candle to the versions which I can find easily in Singapore (think Boon Tong Kee at Balestier Rd, Wee Nam Kee at Novena Ville, Yet Con on Purvis St, Mandarin Chatterbox, Chin Chin at Purvis St, Sin Kee @ Margaret Drive, etc etc).
I was introduced to the most famous KL stalwarts like Nam Heong and Kam Kee (http://chowhound.chow.com/topics/785964), but the rice served there were dry, bland and definitely worse than even the worst chicken rice I'd had ANYWHERE in Singapore!
The best Hainanese chicken rice I'd tasted in Malaysia, in fact, were from Malacca, Penang, Ipoh, and (surprise, surprise) Kota Bharu, Kelantan.
Anyway, a well-meaning office colleague took me to Restoran Ng Kim, this old-style Hakka-owned (not Hainanese, hmm) chicken rice spot in Seri Kembangan today. The roast chicken was delightful, the roast pork was nice but not of Wong Kee's standard (http://chowhound.chow.com/topics/754791) and the barbecued char-siu was respectable, though still lagging far behind Soo Kee's (http://chowhound.chow.com/topics/779322).
The rice was, as I'd feared, pretty plain, with none of the fragrance I'd expected of Singapore-style Hainanese chicken rice. In fact, it was more similar to versions in HK, or Chinatowns in Sydney & London.