In reply to Jon Stewart:
> > I think to climb e4 comfortably you want to be onsighting at least7b on bolts,just my opinion.
> Sounds a bit extreme - isn't E4 normally about f6c/+ ?
The whole trad/sport thing is just difficult to convert. Say your highest sport onsight is 6c+/7a; if you're a very good trad climber (quick at placing gear, cool head) then you can climb E4 or even E5. But if you're not so experienced at trad, then yes, you'd want to have some 'grades in hand'.
And even then, it's all bollox - sport grades are usually given to long bolted overhanging limestone routes, which have very little in common with e.g. delicate run-out grit slabs.