Now I'm a Cell freak, so my oppinions are skewed; however...
Right now Cell is one of, if not -the- worst selectable character. Now that doesn't mean he's a bad character to play; this only means that, all characters being equal, he has the most disadvantages. A -permanent- 1.5 x pl increase upon transformation for one. That's total crap... 1.5x alone is bad, but justified. The permanent factor means that he wont gain PL as fast as someone who can change back and forth, as they'll gain the same amount of PL, if not more, while in their previous form. His low PL effects the damage of his attacks as well; he does less damage to characters with higher PLs, and he cannot win most beam struggles the way things are. When the SBC is attached, he wont have that advantage either.
Perfect Cell should be one of, if not -the- most powerful transformation. It should be one of the most difficult to attain, and it should be one of the most rewarding. His power level should (even if only temporarily) surpass those playing Saiyans who have reached SSj2 before him, so long as they've all been dealing out around the same amounts of damage. He should become faster, and possibly gain a couple more attacks (though I don't see why he would need more, unless one was like a big ki blast (alla the one he fired at Gohan, which Gohan shot back into his face). He needs to turn into a very serious character, because his second form just doesn't cut it at all. Cell could have a USSJ-ish transformation option like Trunks's USSJ transformation, where his power level would increase even higher, and his model would become larger, but his speed would be reduced (he used this against Gohan just before 18 was smacked out of his stomach).
This is all just dreaming, but I'd love to see Perfect Cell turn out like the bad ass he is on the show. Form 2 was nothing special, but 3 was massive, and truly something to be feared. Buu and Frieza will get more transformations (unless the team wanted to include a fourth, SSj2-Cell form, as he is when he comes back to life from the blast that killed Goku), and so their final transformations need not be as spectacular. Still, he'd have the disadvantage of being unable to detransform, but at least he'd be a bad ass. And besides, when PL gain after death becomes an option, servers who have it flipped off will also have flipped off the single biggest benefite of being able to detransform, and Cell will be alright.
Let's make Cell worth while, damnit!