I didn't use one when I had kids. I had to ask around to parents and grandparents if they used a baby bottle sterilizer. Most did, some didn't, but they all knew what I was talking about. So, I decided to look into this extra appliance that would sit on your countertop till your infant was about 6 months old.
I came across quite a few different models, slightly different ways to clean baby bottles. Most use steam, but the manner in which they are heated is different. You have the microwave bottle sterilizer, the electric countertop bottle sterilizer or the on the stove bottle sterilizer. All do the same thing sterilize baby bottles.
The microwave sterilizer seems to be the least universal which surprised me. Due to the size differences in microwaves some sterilizers may not fit. Also you must purchase bottles that are microwaveable. BPA is still a concern so look for BPA free baby bottles. Other limits, you have to clean your microwave every time you choose to sterilize bottles. The food in the microwave can leave behind residue which can effect your baby. eg: spicy foods.
The countertop electric sterilizer does take up room on your counter but is easlily accessable when needed. Load up, plug in and wait the appointed time and your done. This to me seems to be the sterilizer that you can take on vacation or to wherever you are going.
Lastly you can boil your bottles on the stove. It is a wise choice to use a designated pot. To sterilize the bottles, rings, and nipples you will boil for 10 minutes then set out on a rack to cool off, being careful when you handle cuz these are HOT. A side effect of boiling means your nipples will get gummy sooner and you will have to replace them.
You can register at any local department or baby store for a baby bottle sterilizer.