The phrase "is comfortable" is commonly used to describe a feeling of ease and contentment. However, if you're looking to add a bit of variety to your vocabulary, there are plenty of synonyms to choose from. Some examples include: relaxed, cozy, snug, at ease, contented, tranquil, peaceful, snug, homely, and safe. Depending on the context in which the phrase is being used, each of these alternatives can offer a slightly different shade of meaning, providing you with a more nuanced way of expressing yourself. By incorporating these synonyms into your writing or conversation, you can add depth and dimension to your language and convey your thoughts in a more precise and impactful way.