Handcent will easily send SMS, but will not send MMS. It receives MMS just fine. This was a problem on my Photon Q, which has been replaced by a Nexus 5. On the Q, I just used the built-in app to send MMS. This is a bigger PITA with the N5 because of the requirement that you choose a default messaging app. Hangouts sends MMS just fine. But you have to go through the rigmarole of changing the default messaging app, and changing it back again. Handcent will let you send to an email address without inviting someone to Hangouts, and when you're sending to multiple recipients, it is useful to just send from one app.
Anyway, this is not fatal, but I am pretty certain it worked when I was on Sprint. I keep thinking there is some setting that is mucked up. In Handcent Settings-Application settings-MMS settings, I've entered mms.plspictures.com and the proxy and port settings in use in the system settings, but no luck. Handcent has just updated to support KitKat, but still no luck.
Handcent has some really useful features, including handling SMS from email addresses or short codes in the same way as a true SMS - for both alerting and ignoring. I'd really like to keep it.
I have access to an old Droid 2 Global running on PagePlus. I just installed Handcent on it, and was able to send MMS with no problem whatsoever.