Since you are looking for pro's and con's, let me say that I'm not a big fan of 'Rappan Athuk'.
Con's
1) It's designed to be a pure 'campaign in a dungeon', which is not in my opinion a good introduction for new players because it's not diverse enough. Not every player really loves dungeon crawls. You may luck into a group that that is all they want to do and it might serve you well, but if you don't, then its setting your campaign up to fail.
2) It's a meat grinder. Expect a very high body count from new players.
3) It's more 'old school' than the 'old school' modules really were. It's got plenty of 1st edition feel, but very little else going for it IMO. It's pure combat, usually with highly advanced and customized NPC's, often in lethal environments. As an example of NPC design using the 3rd edition rules, it's pretty sweet, but as an example of dungeon design I found it pretty terrible.
I think you are better off with 'Lost City of Barakis'. It's a more varied introduction to the game, is less brutal, and it will give you time to get to know your players before forcing them into a major quest. You can run some sidetreks, or even sidetrek the entire campaign, and then come back to the major plot line when you want it (advancing the big baddies as needed).