Upright pianos range in size from about 36" to 52." Generally speaking, the higher the piano, the longer the speaking length of the strings will be and the longer the strings, the better the tone quality. Generally, Studio uprights tend to be more expensive because they're made of more durable materials to be used constantly (as in a studio).
If you're looking for a grand piano, anything less than 5' is considered a baby grand. A full size upright will have the same string speaking length so you're not gaining anything in terms of sound quality. You do gain the grand piano action though which may be worth the extra expense for a grand.
There are a lot of different manufacturers. The best thing to do is go to some show rooms and try them out to see what you like because it really is a personal decision. The absolute best is a German company called Boethius but they're fantastically expensive. Most people are familiar with the second best, Steinway and Sons. If you're buying used though, don't buy a Steinway from the 50's-70's because they made poor pianos during that time. Also, many companies produces pianos under several names.
Here are a few to consider:
Yamaha
Young Chang
Kawai
Baldwin
If' you're serious about buying a piano, go to Barnesandnoble.com or Amazon and get "The Piano Book" ($18) and "2006-2007 Annual Supplement to the Piano Book" ($12) because that will tell you absolutely EVERYTHING you need to know about buying a piano.