I have 5 characters with this title and you do get some small but helpful rewards. However you do not get any stat bonuses other than the normal gains attained for the class when leveling up.
1) Every survival title earned at 5, 10, 14, 17, and 20th level gives you a chunk of bonus XP. At 20th I got close to 1000xp for getting the title.
2) The Undying title generally is a nice "heads up" to other players that you know how to play that class very well and you'd be a great addition to any party.
** TIP: Your Destiny Points you earn beginning at 10th level are a shared pool for all your toons. So they carry over even if you re-roll for whatever reason. Keep this in mind if you die at 9th level and want to reroll to get the Undying title because it will benefit your Destiny pool to get 10th before rerolling.
** TIP: To get the Undying title more easily, stick to smart groups or avoid any tough areas and boss fights while soloing. It also helps to hop between the starting areas of Ered Luin, Combe, and The Shire to complete lots of lower level quests in bulk. Then move onto Breetown after 14th and the LoneLands after 17th (huge XP rewards).
Generally, I go back and finish off any necessary quests and deeds after I hit the 20th level title.