Well Yahoo doesn't have very good support at all, sometimes NONE. They say they offer 24/7 but there never available. Also ive heard reports people getting charged $1.00 more. Also I know they don't have a transfer function, so I don't know if you can even transfer out. So when they raise the price back up to 9.95 you will have to pay to reregister again. (just guessing on that)
You can transfer out of Yahoo, and that should be done well in advance of renewal. Some people report difficulties, and that is where Yahoo's poor support can turn a simple problem into a struggle. Consider the value of your time, and maybe the $2.99 domain is not such a bargain.
Yahoo probably automatically works well enough most of the time. If it didn't they wouldn't get enough renewals to make a profit.