Playing on Nostalrius has been worthwhile for me, and I do not regret coming here. I have never had any lag, and most of the times I have been disconnected has turned out to be a problem with my internet, not with the servers. Even then, being disconnected is rare. There are very few bugs, and the ones I have encountered have not been serious. The staff is always working to fix them, and improve everybody's experience.
The two servers are Nostalrius Begins PvP, and Nostalrius Begins PvE. Both follow the same timeline and recieve the same updates and maintenance. Which one you choose is largely a matter of preference. The PvP server has been released the longest, and has the most players. However, many people do not like its crowdedness and forced PvP combat. If you go there, be prepared for some competition with other players, and some harassment in contested zones. The PvE server is newly released, and has a population cap of 2,500 players. Here, you are not flagged for PvP combat unless you so choose. The smaller population allows for more flexibility while leveling, as you are less likely to encounter people who are competing for the same kills and resources as you.
There are griefers on both servers, but they do not speak for the rest of the community. Kind people are not unheard of here, and you can find them if you just know where to look. I myself have met quite a few, and they have always been mature and helpful.
If you decide to stay here and give Nostalrius a try, then I wish you the best of luck. I hope you find the experience to be both positive and enlightening.
Best of journeys in Azeroth, and may nature bless you.