[matthew]

Perspective correction is about the only thing I use photoshop for these days, but it's also one of my favourite tools. (I use the filter>distort>lens-correction method.) I think these have worked very well; perhaps a difficulty with #3 may be that the original subject may not be square and straight itself. But looking at the buildings beyond the window, it looks like some rotation and/or shift might still be needed. Otherwise these look good. The only general advice I have is that the PC controls in photoshop aren't as powerful as they look, and they're no replacement for good camera control in the very beginning.

#4 is frustrating. I wish that the figure in the middle either wasn't visible, leaving just the figures on the right, or would step out where he could be a centre of interest. As it is the statue is hiding behind the cross, and nothing quite feels sorted out.

To me #1 is the star of the group, and this photo could really reward some more work. Perspective correction would make it feel more natural, and I'd like to see the darks pulled down to give a longer gradation to the shadows. I'm not sure if this has me disagreeing with Zig, but I'd like to see the whole interior a little darker and moodier.