I've been playing Realms for nearly ten years. It was the first MUD I ever tried, and I stuck with it ever since. I have a tendency to jump around MUDs frequently, and I have only been able to find two others (out of at least 50) that held my interest for anywhere over a few months. All MUDs are the same when it comes to reviewing them: you'll have the die-hards, and you'll have the haters, so don't let the few bad reviews discourage you.
I want to start off by saying that Realms definitely is not for everyone. The game wasn't nearly as big, either playerwise or roomwise, when I started, and it was still difficult to figure a lot of things out. After shopping around other muds, though, I found that Realms was the most intuitive game out there, and one of the more friendly ones for newbies.
Despite its size, or maybe because of it, Realms is a good environment for new players. There are help files for literally everything you could think of, and whatever they can't cover, one of the players probably can. There are a few different ways for new players to get help, most notably the Newbie Council, a group of avatars dedicated to helping characters up to level 25 with information, corpse retrieval, and tips about where to go to gain experience. There is also a built-in hints system, which can get spammy and tiresome quickly, but shows user-submitted hints that can benefit new players. Finally, the immortals are usually active, and are willing to help resolve a new player's needs quickly. New immortals are raised every few months, usually based on their knowledge of the game and their willingness to share it.
When a new player thinks that s/he has a basic understanding of the game, the journey starts. There are many areas for players of all levels to explore. Even when you reach level 50, which is not easy for newbies, there is a whole new world unlocked. Avatars don't lose experience upon death, so there really isn't anything to lose by going out and looking for new things to do.
If activity and twinking isn't really your thing, the social environment on Realms is usually active. There are public and private channels of all kinds, so you can usually find somebody to talk to about anything. There are also player-run bots, which offer everything from spell-up services, to item selling, to a full casino. In short, there is always something for you to do.
Some of the knocks against Realms are that it is too big, or too unfriendly to true newbies, or any other number of things. The MUD has over 150 unique areas, with well over 20,000 rooms. New areas are released regularly, all built by current players. Realms is the original SMAUG MUD, and is always developing new code based on player suggestions. New players start all the time, so it is easy to find someone and team up with them to work together. It's true that a lot of the older players are somewhat hostile to newbies (I know I'm personally guilty of this, but I stay off a lot of channels and don't bug anyone who doesn't bug me), but they are balanced by those who enjoy seeing new players do well.
Realms is not for everybody. It is a challenge for new players, so if you are looking for one then I definitely recommend checking us out. If you're just looking for an easy way to the top, don't bother with us. There are a lot of smaller MUDs out there to get a start on. But whenever you're ready for us, we'll be waiting.