I've been meaning to post a review of this character for a couple days now, but kept getting distracted. Now is as good a time as any, I suppose.
This is the best add-on character Wad I have ever played.
Now, that's not to say it's perfect. But I had more fun with this wad than any other fan made character wad I've tried out. Hell, I had more than playing as Knuckles/Chuckles.
First, I'll go through stats. Jasper controls wonderfully. He doesn't quite reach Sonic's top speed, but his higher rate of acceleration makes up for that, making him a character that is fun just to move around with. His special abilities just add to that aspect of his character.
Shooting Star is a great ability, and well balanced. Being able to jump five times in the air leads to a lot of fun sequence breaking moments without slowing things down to a crawl like playing as Knuckles or Tails might. Because of the high rate of acceleration, you can really go places with this move. I also like how the move puts you in a vulnerable state, for balancing purposes.
There are some negatives to Shooting Star, though. First, I don't see the need for the recharging star meter. The biggest issue that a Sonic game should curb is forcing the player to stand still and wait for something to happen. There are times when challenging level and boss design need to do that, and it's fine, but it shouldn't be a part of a character's gameplay. I don't think it would break or make Jasper unbalanced if he immediately regained all 5 stars upon touching the ground. While I haven't encountered all that many opportunities where I had to sit and wait for my stars to recharge, it did happen enough times that I could call it an issue, and did kill me once as well.
The second issue I have with Shooting Star is much more immature; the move just kind of looks like he's shitting out stars. :P Perhaps if more stars were shot towards the ground, and in multiple directions, it would not only be more useful for hitting enemies, but not look as silly.
Moving on, Spark Burst is a move that I didn't see the purpose of at first, but grew on me as time went by. It actually compliments Shooting Star perfectly. In Shooting Star, you are left vulnerable to damage, leaving Spark Burst as your only method of defense. There's a degree of risk to using it, too, because you lose all momentum in the process, which can be deadly over a pit. It's just good balancing, and I appreciate the thought that went into it. I also found the Burst useful for boss fight; there's no rebound from hitting a boss with the Burst, which lets you keep on their tail and dish out the damage very easily if you can keep yourself at the right distance.
I haven't played with the voice version, and have not collected all 7 chaos emeralds with Jasper (SRB2 doesn't save files that use custom characters for me; is that normal?), so I can't comment on that at the moment. Spark Burst turning into a stomp and Shooting Star gaining infinite shots sounds like a good super form, though.
Lastly, and with some trepidation, I must talk about the character's appearance. I don't have a way of sugarcoating it, so I'll just come out and say that Jasper is not an appealing character design to me. He kind of looks like what you'd get if you mixed a typical Sonic fan character with Kirby-esque simplicity. It leaves him looking a bit like a slime creature with white accents.
The sprites, while servicable, are poorly shaded and at times confusing to look at as well. I don't quite understand what is going on with Jasper's pants and shoes in most of his animations, and the perspective of his hat's rim is poor, which makes its bobbing animation look even more awkward. I'd also question whether both sides of his muzzle fur should be visible in his 'behind the back, running diagonally' pose. The Tails sprites in the game do not have the muzzle showing on the side of his face that is not directed at the camera, and I think that looks better. On the positive side, Jasper's jumping and spinning sprites are spot-on.
Lastly, and I apologize for ending on another criticism, but the pink star effect for the spin-dash is way too big. It's a neat effect, but it obscures too much of the action onscreen. If it was just a little smaller, and maybe a bit more transparent, so that Jasper can be seen from within it, it'd be perfect.
Well, that's my review. As I said, I love playing as this character. Most of the flaws I've mentioned are just aesthetic, which doesn't impact enjoyability in any meaningful way. Even the few mechanical issues I brought up haven't stopped me from having fun, and I won't be disappointed if they are left unchanged.
Very good work, Jasper. :)