Hi Dakota123, Buzz here. I'm thinking it depends what airplane you're flying.
I'm fond of Champs and Cubs, they don't come with flaps (well, the Super Cubs do) so we slip to dump excess altitude most of the time. And Crosswind landings are always in a slip for me, when landing a taildragger you -really- need to keep the runway,prop,tail all in a line. If you crab when you touch down you'll ground loop and end up where the nose was pointing (after an exciting ride).
So... in an Aeronca Champ the airspeed indicator gets inaccurate, but that's not a big problem on final (yeah, right.) because my eyes are outside. I'll start final approach at 60-65 mph, keeping extra altitude (engine failure in the pattern, can I at least get inside the airport fence?)
On short final, I'll do a forward slip to dump the excess altitude. Sometimes I've seen more or less 45 mph (Vs is 38) and feel a lot of buffeting if I'm at full travel on the rudder and stick. But it only takes about a wingspan of altitude loss to recover once you neutralize the controls. A few times I've kept my approach speed high (75 mph -almost cruise speed) and slipped, target speed over the fence is 55 mph. That's worked also.
On the Champs and Cubs, if I were to stall in a slip, the wing unloads. So the aileron input neutralizes, but the rudder input is still quite strong. So you end up with the wings leveling and you wonder why you've got all that yaw... many tailwheel pilots become sensitive with our feet. If I were to stall with a Skid... that's how you start a spin. (another topic, everybody should learn how)
The Cessna's POH admonishes the pilot not to slip with flaps deployed - under some circumstances the nose is supposed to bobble up and down. I'm thinking it's also hard on the flap attach brackets (thinking as an aircraft mechanic)
Notice on the C-150 series aircraft, the Static port is on the left forward fuselage. If you were to left slip, then the static port is now in an area of high (impact) pressure instead of neutral pressure. On the Champ it's on a tube out on the strut, and has 3 or 4 microscopic holes to try and get a neutral reading.
One factor in not paying strict attention to the airspeed is that I've got my eyes outside looking for other traffic, looking to see what the wind is doing to me. I'm flying trimmed, using attitude, and control pressures to deal with my airspeed. In a slip, I do have to hold the controls there - the Champs and Cubs really want to return to neutral and whatever speed they were trimmed for.
And all this might not apply to a modern, high tech airplane.