We started off with a full-size high chair and quickly realized that we made a mistake. The BEST high chair that I can recommend is the Fisher Price Space Saver high chair. It is great because it does everything a full-size highchair does (even reclines for infants), but it's also portable (to take to grandma's house), it converts to a booster seat, and it fastens to one of your chairs, so it doesn't take up extra space in your kitchen.
My son is 2 and STILL loves his chair. Best thing on the market, in my opinion.
JGM281207:I think anything could scratch floors, you just have to get those stick on pads for the bottoms.
this.. or you can get one of those splat mats to put under it just for the purpose of not scratching.. (because i've used these mats for my niece and they are never big enough for anything else)