If you've played past Castlevania games, you should enjoy this one, as it's basically just one big montage of characters, levels, enemies, music etc. from the past games. So it really gives you that feeling of nostalgia.
To be honest though, the only replayablility to be had with this game is in farming for items (killing the same enemy/boss numerous times for a particular piece of gear) and leveling up sub-weapons.
If the game never goes on sale and one day you do decide to get it - you'll be lucky to find many games if you don't have the dlc levels. The only people really playing this now are the veterans who want to beat the levels in the best times, or are after that last piece of gear - meaning that if you play with randoms, you'll most likely be beating the same level over and over again in under a few minutes, for the next 30 minutes. So you won't really get any enjoyment in playing with randoms - so you'll want to look on forums for someone to play with, or try and get some friends to play the game online with you.