It's a neverending battle, right? Hard to draw the line between phones that deserve having a data plan at all, versus phones that can't possibly make good use of one...the Replenish to my knowledge is the only Sprint phone with Android that doesn't need the $10 Premium Data riser. In terms of features I believe this to be appropriate, but as an entry-level phone it's probably better than anything that doesn't need the $10 riser. A pity you can't forego the data plan and use these new phones with just WiFi.
I have actually been considering the Replenish for my brother who is switching networks soon. He has few needs, and this phone is still far ahead of his old Nokia brick. The solar case option would be nice because he spends a lot of time outside and is notorious for leaving the charger in another state. Mostly it would have to make calls and handle texting, he doesn't need music and probably wouldn't use the camera. He has a big laptop and is farsighted, so maybe he'll grab another feature phone after all. >.>
Selfishly I might bully him into also getting the Echo just like me. Telenav is much better than his Garmin, and the software keyboard is bigger than the Replenish's hardware keyboard. There's a spare battery/booster included. Camera is better 5Mp(tolerable) vs 2Mp(tolerable) / 720p video vs 480p, and it has FIVE TIMES more pixels PER SCREEN. Talk time is two hours longer, another plus. But mostly I have the same phone so I can show him where everything is and answer any questions that come up.
So...the Echo is probably the best "Premium Data" phone you can get for $0, and the Replenish is probably the best semi-smart phone you can get without paying the extra $10/mo. Decisions, decisions...