Due to the timing of our trip, taxis were in short supply in KL. To be safe, we stuck to the KLIA Ekspres which we found to be incredibly convenient - once you get to it. We used the monorail to connect from our hotel to the train - which took a bit of time. However, the train service itself is great. The tickets are a bit pricey so if you're a family of three or more, a taxi is still cheaper. But, if you're interested in avoiding traffic and reducing your carbon footprint, this is a great call.
ONE COMPLAINT: This train also carries passengers between the two terminals at KLIA - for a small fee. When we asked as the train desk if there was no free way to travel between terminals, they told us NO. There is a free bus. I'm not a fan of companies lying to encourage increased patronage.