I'm just a hobbyist and Xn Producer is way more than I need anyway, but at $99 just for Melodyne Essential (Celemony's website price) the $149 to step up to X3 seems like a pretty good value.  I've been wanting Melodyne for awhile to experiment with vocal harmonies.
 
Of course, I don't like the upgrade game any more than the next person and my wallet is lighter to be sure, but what the hey, it's always fun to get something new.

Melodyne Essential, in my humble opinion, is not worth it. It is a gesture to replace V-Vocal and while Melodyne does sound better and is beautifully integrated, the "Essential" edition misses some vital tools like the pitch drift tool and the formant editing tool. Both of which operations were available through V-Vocal if implemented slightly differently.

However, getting Essential means you get 100 bucks off the Melodyne Editor (or if you really can do with less, Assistant). I just caved and bought Editor, which I'm sure is what Celemony's idea was with supplying this deal.

ARA in X3 is the big deal. It offers a lot better plugin integration. Not to mention VST3. 
 
 
Edit, the above is badly written. VST3 is not due to ARA. It is just a nice addition. 

Sanderxpander
Melodyne Essential, in my humble opinion, is not worth it. It is a gesture to replace V-Vocal and while Melodyne does sound better and is beautifully integrated, the "Essential" edition misses some vital tools like the pitch drift tool and the formant editing tool. Both of which operations were available through V-Vocal if implemented slightly differently.

However, getting Essential means you get 100 bucks off the Melodyne Editor (or if you really can do with less, Assistant). I just caved and bought Editor, which I'm sure is what Celemony's idea was with supplying this deal.

a +1 to this.
 
I have editor already and certainly looking forward to tighter integration using ARA

Mystic38
a +1 to this. I have editor already and certainly looking forward to tighter integration using ARA

It really seems very slick so far! Very close to SHIFT-V for V-Vocal and I always liked Melodyne's interface a LOT better than V-Vocal's. I used Melodyne while working at another studio but could never justify the cost at my much smaller home project/vocal studio, already having V-Vocal "for free". Really happy I finally bit the bullet and especially now that it's integrated so perfectly. Really feels like part of Sonar.

I have been using Melodyne Editor for some time now.  It is a great tool for editing audio.  I use it to tune up vocals, guitars, bass, convert audio to midi (try that on a rthym guitar part and add a synth to the midi chords), and you can edit individual notes within a chord (piano, guitar, etc.).  
 
If you don't know its capabilities, you should watch the excellent videos available on the Celemony site.  Editor is awesome and the ARRA integration is wonderful.
 
Rimshot