money wise they'll cost as much as any other twink for gems and enchants. pvp gear you get by pvping and even starting at 58/60 you can get enough pvp to get a full brutal set + weapons in 10 lvls if you just do a lot of pvp (time consuming, but at least you can ding and be geared...make sure to get a lot of extra honor for the pvp bracers, belt, boot, neck, trinket, rings)
skill wise? idk i dont like the one dk ive made very much...its still like 62, i just dont really like the feel of it, the rotation, anything...but im sure for some people its pretty easy to get a handle on. the funny thing is ive raided as a feral druid for years and never missed a beat with the rotation even though at certain points in time it has been regarded as the hardest rotation, somethings are weird like that.
and against other players they can be pretty devastating depending on your skill, class playing against, situation (bg/arena/world), etc. but i think they hold their own very well and have a well rounded tool kit of cool downs depending on spec