I have stayed in Impiana KLCC for a number of times and it is hard to find fault with this hotel. Aside from Mandarin Oriental and Traders Hotel, Impiana KLCC is on top of my list.
My latest stay was in a superior room with a queen sized bed. The room was okay although I am not too keen with the shower head inside the bath tub as there is no separate shower. The front desk was helpful enough to quickly sort my room as my son was crying hard. The parking was adequate at nights but you may have to use the parking underneath Traders hotel during the day due to full parking.