Yes, everyone knows breast milk is best for a baby, and trust me I wouldn't dare argue about that. However, for any number of reasons a lot of moms can not always nurse their children, be it for medical or financial reasons, or personal preference. But there is no reason a mom must feel guilty for not nursing her child. As long as your baby is receiving proper nourishment, love, and attention you are being a good mother and let no one tell you differently.
People will tell you giving your baby a bottle, even one with breast milk, is a disservice to your baby. They will tell you that you obviously didn't try hard enough to nurse and that by giving your baby a bottle you are missing out on developing a special connection, or bond, that of course you can only get from nursing. This can make many a new mother who does not nurse feel guilty and like a failure, especially if they had wanted to nurse but are unable to. I could not nurse my middle child, Ryan, due to milk supply issues and his own reflux and metabolism issues. I felt horrible because I wanted so badly to let him nurse, but by the time he was 2 or 3 months old my milk had completely dried up. When I realized I was no longer even producing milk I became greatly depressed, and it didn't help that my own aunt, who nursed all three of her daughters until they were three (or close to), accused me of "just not caring hard enough to try." I've never suffered a bigger physical or metaphorical slap to my face.
But... mothers who can not nurse should not fret! You can still develop a close bond with your baby while using a bottle. Its as simple as it is to develop one through nursing. When feeding your baby focus on your baby. Try not to let yourself be distracted the entire time by other issues. I'm not saying ignore all else, but let your baby know he/she is important to you and that this time together is special. Look deep into your baby's eyes and talk to them. Even if you are holding a conversation with someone else, look in your baby's eyes or face while talking. If possible, allow as much skin to skin contact as you can while feeding the baby. If its cold just wrap a blanket around the both of you together. These are all the same tips that lactation consultants will tell mother's who nurse to help bond with their baby, and there's no reason why you can not do them also. And the best part about giving your baby a bottle is that Daddy can also bond with the baby using those exact same steps, something that if you were to exclusively breastfeed could not be done.
Remember, you are the mommy, and you know what is best for your child, and as long as you love your baby, give him or her the nourishment needed, and plenty of attention you are being the best mom you can possibly be, and that is all that counts.