I probably should have started with something shorter.
Before I get in to the problems, I want to note one important thing: it's easy to use and I like the UI. I say that as a Final Cut Pro 7 user who found Final Cut Pro X confusing and discombobulating. By comparison, I’ve so far found working with Premiere Pro very easy. The interface and method of working is close enough to Final Cut that I've been able to do this project without spending time reading manuals or watching tutorials. And the U.I. hasn't frustrated me, so I'm really happy about that.
On the other hand, I have had a very perplexing problem with performance. Specifically, jumping from one section to another can sometimes cause the program to take half a second to a minute just to update and display content. I've seen a lot of the media pending window, though I've also spent a lot of time with the program just sitting and thinking.
Consequently, I also spent a lot of time rendering the timeline so that I can preview (and that means, if I make any changes I have to re-render.) Good thing I’m used to working with Final Cut Pro!
I’m still trying to work out why it’s performing so badly, and I need to spend some time trying to “debug” the problem (last week I was just trying to get the first cut done the best I could.) It is using five tracks with a mix of content (1080 30p, 60i and some HDV.) I spoke with an Adobe engineer at the BOSCPUG meeting last week and he assured me that those formats shouldn’t cause a problem. It might be that I’m using an iMac that needs more memory. I’m working on changing that too.
About that GPU
One other odd thing, which may or may not be related. The software seems unsure about whether I have a supported GPU (I’m pretty sure I don’t, because officially Adobe only supports MacBooks…)
Yet it’s shown the selection for the GPU a couple of times, and then it later objected when opening a project, saying that the GPU had previously been selected, but was not available. I'm not sure what’s up with that (and no, I did not try and do the "fix" that fools Premiere into thinking the system is supported.)
UPDATE: Paul Joy has written about some performance issues with Premiere too. He talks about a somewhat similar problem in CS5.5, though suggests those are fixed in CS 6. I haven't seen the problems he talks about in CS6: Premiere Pro reliability – doing things by halves
For me CS5.5 on Lion got to the point of being fairly stable, it’s weakness continued to be handling projects with a lot of media, I found that scrubbing through a timeline with hundreds of short clips would always result in playback problems so learned to not demand too much from it and avoided scrubbing through clip heavy timelines.
[...]when working on a large project I would often see the ‘A Serious Error has Occurred and Premiere needs to close’ message many times throughout each day.