As you become a better cyclist then you will start riding with better cyclists and therefore be exposed to more advanced techniques than you were when you first started riding. One of the most common upgrades that a cyclist makes as they advance is to begin riding clipless pedals. If you aren't familiar with a clipless pedal then basically what it consists of is a cleat of sort that basically "anchors" your foot to the pedal and they make the best Mountain Bike Pedals.
Advantages of ClipLess Pedals
The biggest advantage to a clipless pedal is that it allows you to be a much more efficient cyclist. By anchoring your feet to your pedals, this allows you to utilize the "upstroke" of the revolution as well. Most cyclists power the bicycle on the down stroke only but by being anchored to the pedal then the cyclist can pull UP on the pedal with one foot while the other foot is pushing DOWN on the down stroke.
This may not sound like it would make much of a difference but I can tell you that the power and speed increases that you gain from learning to ride clipless properly are WELL worth the effort involved with learning to ride this way. If you were to take two cyclists of the same ability and conditioning level and have one ride clipless properly and the other ride normal pedal, then the clipless rider is going to leave the other in the dust. It will be almost embarrassing.
The Cons of Riding Clipless
There are definitely some cons to converting to clipless pedals for sure, the main being cost. You need a special set of shoes that are designed for clipless pedals first and then of course you need the pedals. The costs range from affordable to ridiculous depending on how high quality and how snooty you want to get with your equipment. A decent set of entry level pedals will run you about $50 to $100 dollars and the same goes for the shoes, so you will have $100 to $200 dollars invested to start riding clipless.
The other con involved is simply the time involved in learning to ride this way. You need to master the entry and exit of the pedal, clipping in and clipping out when you come to a stop so you don't fall over. You also need to master the upstroke technique if you are going to truly reap the benefits of riding clipless.
Clipless Pedal Recommendation
If you are not sure what kind of pedal to start out with then you can always get advice at your local bike shop but I can tell you from years of experience, one of the most popular and user friendly pedals are those from Shimano. Shimano pedals are user friendly, adjustable and work extremely well. A Shimano PD-540 Mountain Bike Pedal makes for a great first pedal.