Hi again, Giles, good idea to split up your post into various ones and distribute them into their respective forums, I might as well move one other of your threads that's sitting in General right now over to here.
As to critique, well, the first two look technically correct, very nice subjects, too, well focused, nice colours and adequate contrasts.
The middle two are not quite in focus, they are a bit soft (with macro that should not happen, is my idea of macro photography) and lack in contrasts, too, mostly so that little bug or centipede or whatever that is.
For the last I would wish for some more DOF (depth of field) ... I don't mind that the letters become blurred towards the background, but personally (mind, this is a very subjective thing!) I would have liked to also the see first letter in focus. But that is just me, others might think differently about this.
These have all been taken with my digital, which has an auto focus but a really good macro feature. Still, I have real problems trying to control the focus. I love using depth of field well in macros, but I can't because I have no macro lens for my SLR(Pentax K1000). If i did you would see some amazing macros.
Yes I also agree with you on the one with the old camera. It wouls have been better if it was perfectly sharp on the left, but it''s still O. I have since given it away. So no hope of a second chance(the old camera).
You might want to explore the "reverse lens technique" for macros (though it is a lot of try and error for a film SLR and the slow feedback you get on your attempts), I took some of a dandelioin the other day with the lens reversed (explanation in this_thread, scroll a bit, there are more a bit further down), you might want to go take a look, if you are interested in macro?
Or some in the Themes, right_here.