I used Handcent for a long time, then when the X came out it started having problems. I switched to Chomp, I loved the options, I paid for it.
Then handcent updated, it now matches what I had with Chomp, but for free. With the most recent update to handcent Chomp no longer has any advantages and handcent is free with no big ad on your conversation list
I am back to handcent, even though I already paid to eliminate ads in Chomp
So far nothing else compares. If all you want is a pop up, handcent's pop up is nice and has lots of options