I can say from our experience with people reporting, that people who run on low-cost or free shared hosting will experience slowness due to those servers having one of the following:
* being overpopulated with other shared accounts and not able to handle processing
* having suhosin improperly setup (which is documented in
RTFM)
* having too strict open_basedir restrictions for most apps
* having improperly setup symlinks on the server
* running on buggy mysql versions (such as 5.0.51a)
* running on buggy PHP versions (5.1.6/5.2.0, or really anything pre-5.2.6 these days is a bad idea)
And etc. On the mgr side, running the manager in IE is going to be slower, because IE is a slow browser. Also, running the mgr in Firefox with a lot of extensions will be slower, because Firefox slows down with lots of extensions. We recommend a vanilla Chrome install for optimal usage, but Firefox and Safari work fine as well.
Also, if you have to disable the "compress_css" and "compress_js" settings in the manager, your manager will run slower. You should only have to disable these if you have an improperly setup or too restrictive environment that is causing issues with minify.
[ed. note: splittingred last edited this post 14 years, 5 months ago.]