you can go to www.tripadvisor.com to check for comments on Ibis. From that web, ppl says it is the standard Ibis (small room but clean) but quite a walk from MRT... but then at $640, I think that's a good deal too!
I also booked tickets first, then booked this hotel; unluckily after that a hotel package (air tickets + hotel) seen in singapore air holiday!!! If I book this package, I can save HK$800