I have all skins downloaded and installed.
AND im using custom sounds with my onboard sound.
That being said I have a newer machine built less then 6 months ago using some of the best parts I could find at their price.
Pretty fast CPU (8400 running at 3.0) pretty fast ram. and a fast hard drive (Caviar black)
And I have partitioned part of that hard drive to be dedicated almost exclusively to AH.
I do occasionally get..not a stutter but an ever so slight pause I have been able to attribute to skins loading
I attribute my lack of problems to the parts I chose and to running a fairly clean machine.
Havent had any problems with the sounds. But I do have a soundcard standing by that I will install the very first time I encounter any
So as not to get anyones hopes up. In over 10 years of playing online sims First Airwarrior, then for the last 6 years or so AH.
This is the FIRST machine I've had thats run any of them near flawlessly. And I've been through no less then 5 computers including this one.
I attribute my success with
The agonizing over each individual part I put into this build. (with no small help coming from the AH community)
A clean install of my OS.
Keeping a clean machine without an excessive amount of background tasks running
And quite a bit of luck.
So if you go by the amount of luck I've had. you stand a 1 in 5 chance of being able to run the game flawlessly

So while its possible. Its not always very likely
That being said. And to get back on topic that Skuzzy hijacked

(Just bust'n yer chops skuzz)
Down them all is a great addition to firefox.
Even if you dont use all the skins. It makes it far easier to download the ones you want. Be they all, some, or none
Just check the little boxes of what you want and dont check the ones you dont.
Actually you have to do it that way or you download everything on the page,,,literally
But
IMO this is how the download page should be set up to begin with
Instead of having to download each individual skin. Just check the appropriate boxes. And click download