Strictly speaking, the debate about the validity of split infinitives still rages on and using them is more a matter of personal preference than a grammatical no can do.
For my part, as far as solecisms go, I love an occasional split infinitive. Moreover, as Wikipedia sagely reminded me, one of the most famous split infinitives occurs in the opening sequence of the Star Trek television series: to boldly go where no man has gone before! And I say if it works for Captain Kirk, it works for me! :-)
Actually, Wikipedia has a very fair and balanced discussion on the subject. I think this line sums it up best: "Most experts on language now agree that the split infinitive is sometimes appropriate. Those who use it consciously may see it as a form of hyperbaton, and some major poets have employed this to good effect." There! I seem to have won half the battle. Now if only I can finish that epic poem I started... ;-)
Speaking of poets and split infinitives, I would be remiss if I didn't include the Bard's Sonnet 142 here:
Love is my sin, and thy dear virtue hate,
Hate of my sin, grounded on sinful loving:
O! but with mine compare thou thine own state,
And thou shalt find it merits not reproving;
Or, if it do, not from those lips of thine,
That have profan'd their scarlet ornaments
And seal'd false bonds of love as oft as mine,
Robb'd others' beds' revenues of their rents.
Be it lawful I love thee, as thou lov'st those
Whom thine eyes woo as mine importune thee:
Root pity in thy heart, that, when it grows,
Thy pity may deserve to pitied be.
If thou dost seek to have what thou dost hide,
By self-example mayst thou be denied!