What Valve software have you used that is subpar? It must be a lot of it since you said you "generally" find this to be true.
The thing takes several seconds to start on my brand new gaming rig. Not insufferable but given its only usefulness is to list my games and start one, that's a lot.
I think there's a start-up popup you can turn off in the client settings. I've never seen ads other than their storefront, but I want ads there.