That is a really good deal!!
I'm pretty sure the analytical guys at work keep thier pH meters in a storage soln when not in use. They are probably way more precise than our needs.
Still might not hurt to have the replaceable probe and possibly a calibration soon above 7 as well. They'd tell ya that if your calibrated from 4 to 7 you only know it's right between those 2 data points and anything outside is a black box. Again they need to be way more precise than our needs and even that 20 seems like a fantastic deal
I'm just using pH paper at the moment.