I've been using PI for years. Currently, I'm running version 10. I like the program very much, and it provides a LOT of functionality for a small amount of money.
There is no raw support which is bad, and so I bought PSE3 to process raw, and then finish the editing.
Even though PI 10 is much much faster than PI 8, it is still quite slow compared to PSE3. Unsharp mask for example is almost instantaneous in E3, and many seconds in PI 10.
PI 10 has many feature which I love. Functional layers, really nice transform tools, an integrated web page maker, gif animator, plus just about every function you could want to processing photos. One thing I can't stand about E3 is that in order to straighten a tilted photo, you have to do it freehand or draw line and then read and type the angle of the line into the rotate tool. In PI, you have a horizontal and vertical alignment tool that you register and then double-click to make it happen. Much easier than E3.
Part of my problem with E3 is that I'm so used to working with PI, the way it does stuff just seems natural.
I am forcing myself to make the switch to E3 simply because that's where all the information, books, and people's tips are. Fighting the mainstream just isn't worth it.
The neatimage home + plugin works just fine in PI which is really nice.
PI 10 also has a nice lens distortion removal tool.
If you want much more functionality than E3, and you can't afford CS, then PI is great way to go--especially if you don't want to process raw. One way to get around this would be to get a stand-alone RAW converter and then finish the work in PI, but having integration is just much more convenient. For example, until I knew the neatimage plugin worked in PI, I processed noise with the stand-alone program, but it was too tedious--the plugin works so much better. I'm kind of thinking it is that way with RAW too--I'd rather have it work straight away in the photo editor.
Maybe this helps?