CB is great technology and has real advantages to other modes of communication - but reliable comms between two parties is a definite weak area. So it really depends on what you want to do.
The biggest problem with CB is the antenna. If you are running a well-placed dipole, it won't be your antenna, but the other guy's. If they are mobile, you might get a few miles range typically. The main reason is that mobile antennas have so much loading coil that doesn't really add to the ability of the antenna to radiate/receive a signal. The wavelength of CB is roughly 11m, making the ideal antenna about 18ft long - a short mobile antenna is going to be a compromise no matter what. The other problem is most mobile CBers don't tune their antennas and that further reduces the performance. Communicating from base station to base station (say via two dipoles) is going to get you a longer range- but it does vary a lot depending on weather conditions, sun activity etc.
That said, a proper 18ft dipole is going to pull in some great signals when conditions are right- its really one of the best all-around antennas. You will receive, and probably be able to transmit to stations around North America. But exactly who you can talk to won't be reliable. Around sundown conditions are typically best for comms along the daylight/nighttime line. One thing I like to do when camping is string my wire dipole between a couple of trees and see who I can hear. I can normally receive stations up and down the west coast. Equally typical however, is that conditions "aren't right" and I hear nothing at all.
There are a lot of options with CB as well - the best is to get something SSB capable. Single-sideband will give you a lot more range and the receivers in SSB radios tend to be much more sensitive. But the "new" price gets into the territory of Ham radios, and Ham gives you a lot more options for reliable and semi-reliable comms if you're willing to invest the time to get your license.
In summary though, the most important thing is your antenna. A good antenna will provide orders of magnitude better performance. There are guys running amps on their CBs illegally, but a decent antenna will normally provide just as much "performance" without the cost. If you are going to spend a bunch of money on a CB and an amp though, I'd recommend getting a ham license as your equipment costs will be in the same price range.