There's a limited degree to which it's useful in resolving scope and type ambiguities in C or C++, but excessive use could definitely render things much less readable. It doesn't help that some of those letters survived long past their shelf life (ie. 'lp' for long pointer, where in non-segmented architectures there is no far (aka long) and near pointer distinction).

These days in C++ I'd only ever consider using s or g, and never the type specifiers. I also largely consider signalling member variable vs. local variable to be pointless in all its forms (including _ suffix or prefix) now.