There is nothing wrong with a simple battery charger like that. Primarily they protect the battery from over voltage but just realize that they leave a whole lot of energy on the table. With a sophisticated charger you can use a smaller PV array to keep a larger battery fully charged and across deeper discharges. In a word it'll be more efficient.
'91 Pickup - Imelda
'08 Tacoma TRD - Donna
"Hey Macarena!" -- Thomas Jefferson