Your tips Weather-wise KL and Malaysia in general is a hot and humid place and can rain cats and dogs without much warning. Hence be prepared mentally and physically. Travelling should be fun and so leave your attitude (if any) at home. Spontaneity is the essence.
If you wish to climb the Petronas make sure you book the tickets in advance. Personally, I have not done so but generally done with towers.
In terms of shopping in the Petaling Street (Chinatown), we found the adjacent Central Market (although less of a bargain) more appealing - actually recommended by our driver.
Outside the city, Batu Caves may not be for everyone. The stairs can be quite imposing especially on a hot humid day.
I would recommend a side visit to Shah Alam, Putrajaya (Malaysia's Canberra) and while at it, Cyberjaya.
Genting Highlands is a worthwhile visit not just to get away from the City heat but for the lush green surroundings (cable car ride can be a foggy experience), theme park, quality shopping and some stand-up entertainment.
Our next destinations: Penang and Malacca as two starting points in the Peninsula, and not forgetting Sabah and Sarawak in East Malaysia.
KL is a must and "Just do it" destination. Do it for great Malaysian food where variety is the spice; do it for shopping where bargains (Petaling Street) or no bargains (e.g. chic high end stores at the Garden Mall) you come out smiling and satisfied; do it for what Malaysian multiculture has to offer and provide a different perspective. Most of all, consider KL as a hub and gateway to other destinations where only time is the limit.
We have not rated any hotel because we were lucky to stay in a family penthouse apartment with an enviable paranomic view of the Petronas Twin Towers and the KL Towers in the horizon, the new Palace in the foreground, and on a very clear night, the red lighting of the Genting Highland hotel sign. If only I can post a picture.