My question is, is he worth it?
I'll go more into detail. I'm cosidering using Tigurius in my mostly shooty Ultramarines army. He has the same statline and rules as an Epistolary for the most part. With the gear that tigur comes with, you're up to 134 points. The cheapest phsychic power for your second power is 9 points (total 143) and the most expensive is 30 (total 164).
Disadvantages: Cost. If you are going with one of the cheap powers, tigur costs 31 more points than his standard codex breatheren. Also, he cannot be equiped with a jump pack or terminator armor.
Advantages: Selecting powers after deployment. I, personally, think this is amazing. Picking your powers after you see what you have to fight is nice. However, the advantage is somewhat down-played because most players put their libby in a squad based around what powers he has been given. Therefore, this ability losses some of its appeal. Secondly, Hood of Hellfire. Doubled range is extremely nice if I decide to use him as a shooty libby. It also applies to 4 out of the 6 possible powers.