I've been using UE/Mac for nearly 2 months now. Yes. It is noticeably slow. On my computer (
Mac Mini 2.66GHz iCore2 Duo, 8GB 1067MHz DDR3 RAM, 500GB HDD), it is NOT too slow to use, so I'm mostly satisfied with my UE/Mac experience overall. Here are a few things I've noticed.
1. It seems to get much slower with larger files. This is particularly disappointing because UE/Win excels in this arena. On UE/Win, I used to open absolutely HUGE (over 1G) text files that would simply crash other, less capable editors. I don't dare try even getting close to that kind of spec with UE/Mac. I've seen NOTICEABLE slow-downs on my Mac when editing files around 500K in size.
2. I know Macs are supposed to be crash-proof and all that (don't believe it), but it seems that if I open too many apps/files in the OS, it has a direct effect on the speed of the interface within UE. A full reboot is the remedy for this situation. (What's that, Apple? Oh. You mean I have to reboot my Mac every day? I thought that was a Windows feature!) I don't know how to prove this, or recreate it. This just seems to be my experience.
3. There is an option in Preferences->File Handling->Temp Files that allows you to control the usage of "temporary files". The option's wording is very vague, not even bothering to say what "temporary files" are used for. It does say that if you disable it, you could see improved performance. I tried it, and COMPLETELY OBLITERATED my HTTPD.CONF file through a comedy of errors. The changes I made were immediately saved to the file and there was NO WAY TO UNDO.
DON'T DISABLE TEMPORARY FILES. Don't do it. You'll regret it. I don't think I really noticed the "improved performance" anyway, but that could be due to my preoccupation with trying to get my httpd.conf file back.
I'm very seriously considering upgrading to an SSD drive. I have a feeling this will help the overall performance of UE, particularly when it comes to the use of temporary files. Then again, constant updating of temporary files could wear out the SSD prematurely. Who knows? If I ever do upgrade to SSD, I'll let you know how it turns out.