Well, I guess it depends on what you are looking for...berber is very durable, so it doesn't wear out like other kinds of carpet, but I personally think most of it looks like office carpeting or basement carpeting. Although you can get some really pretty berber (my parents have some beautiful berber) but it is usually pretty expensive for the nice looking patterns. Personally, in my next house, I want the track resistant carpeting...it always looks freshly vaccuumed, even after it's been walked on all week. I really hate it when I can see my footprints all over the carpet the second I'm done vacuuming. If allergies are your concern, I would skip carpet all together and put down some kind of hard flooring (hardwood, laminate, vinyl, tile) and put down rugs. Although that presents it's own set of problems, especially hard wood, since it takes a lot of effort to keep it looking nice, and no matter what, it will get scratched and will need to be refinished eventually. Tile and vinyl and less work to maintain, but they don't lend themselves well to room except kitchens, bathrooms and entry ways, in my opinion. Ultimately, you have decide what problems you would rather deal with, because all flooring comes with its share of problems! I hope this helps!
M.