In reply to Oogachooga:
I'm not climbing very hard, but I think grades are only a guide, and not always a very useful guide, to the difficulty of a climb. If you can see the climb (i.e. single pitch), I think it's better to try and make your own judgments in dialogue with the grade/route description/any other opinions to hand, e.g. "oh yeh, it's a well-protected jug-fest" or "a bit bloody stiff that crack". Also, forgive yourself if you're not climbing "as well as you ought to be", drop a grade or two, and just have fun.
Since I started out on pocketed limestone, I tend to find I'm weak at crack climbing, featureless slabs and arêtes with no feet that involve maintaining a lot of body tension; therefore I struggle on grit, which often involves these sort of features. I also find that some features go at easy grades despite a complete lack of protection, e.g. Fag Slab at Brimham is a severe, despite having only one pro placement at about half-height - presumably because the slabby, grippy rock is considered to mitigate this. But, for me, the expectation had built up that a severe should always have good protection, so it threw me out.
Is this sort of climbing harder, or is it just me flailing and whining? I would say, it's objectively harder for me, because of the sort of climb it is, but not necessarily harder for those who cut their teeth on this. I can only take consolation in smirking at the idea that gritstone can become "polished", as someone who's tried bouldering on the Red Wall at Trowbarrow.
It also seems evident that tradition has a central, but equivocal role in grading - grading is no science. For example, it seems to me that chimneys are often graded in the old money, even where they are damp, awkward, strenuous, terrifying to contemplate and lacking in nut protection. Perhaps, prior to the invention of nuts and cams, such green chimney seemed safe and welcoming compared to the face climb around the corner, but clearly it presents a different sort of challenge... On the other hand, witness the ridiculousness of retroactively re-grading the classic mountain route Bowfell Buttress as Hard Severe because of one short crux section, when it stood at VDiff for many years and was originally graded Diff: when the mountains start moving, the whole grade system wobbles.
One problem, I think, is differing opinions about what the grade system is fundamentally about:
1. Safety: knowing what you're getting yourself in for.
2. Competition: gauging relative levels of achievement.
3. Braggery: misrepresenting climbs as easier (or harder) than they are (or one's climbing as better than it is).
4. Tradition: one method of communicating about climbing across time and space (including character and achievement)
All these considerations come into the mix, as well as local climbing cultures, which lead to distinctive experiences at different crags, and first ascensionists (e.g. Allan Austin was obviously a hard bastard, and even his low-grade routes are not to be taken lightly...).