Gifford is thorough as hell.
Might offer access to too much information for a first time reader (which I was). As I got further into the novel I consulted this book less and enjoyed the reading experience more. This book is great, but there's so much here that I think it interrupted the flow of reading too much.
Still - so many cultural references in Ulysses. So many songs and the whole of Irish political history. So many languages and so many allusions. Gifford offers important access to all of this information.
So. Much. Information.