I bought my s/h mint condition 30D in Spring 2007 and to start with it was used with my mint condition EF 300 f4L, & an outwardly battered EF 300 f2.8L, and with 1.4x & 2x Canon extenders - primarily shooting wildfowl on water from a sturdy tripod. Later it was used with a mint EF 300 f2.8L IS USM.
It's taken some time sorting out the focus problems which were largely front focus errors when used with the old 300 f2.8L; a lens which had initially seemed OK on my 5D. After analysing hundreds of shots & doing simple statistics I decided the lens was front focusing, and after getting the 300 f2.8L fixed (a tale in itself due to its age) I was still not getting the results I expected, so I went over to using the 5D with the 300 f2.8L & 2x. These were better despite losing the 1.6x factor.
Last autumn, I had Lehmanns check the 30D and correct its AF, and recent results with my EF 300 f4L have been fine. I must now check it again with the 300 f2.8L lenses. Thank goodness I'm not using film!
OK I have had some very good results but too many "easy shots" on bird targets were significantly front focused. Was it mis-alignment between the v/f centre focus spot and the AF sensor (picking up on the nearer water), or an AF body-lens problem? Seems like I may have had both, and it's taken around a year to get it sorted and have confidence again in my gear. (I had both lens and body adjusted independently, as I didn't want to lose the good AF accuracy which I got with other lenses and different extended subjects.)
I've just ordered a 1D MkIII so that I can take advantage of the Micro-adjustment facility, and am hoping that in future the errors will be mine rather than from the equipment.
I bought my EF 70-200 f4L in May 2007 for 430, after much checking of web reviews and prices. Normally I buy 2nd. hand, and have had very few problems buying a dozen lenses over more than a decade of using Canon. I prefer and use primes on my 5D, but after taking my EF80-200 f4.5-5.6 to the Dolomites, I felt that a quality zoom should give better results. In view of the mixed reviews I found on the web, this time I bought new and returned my first copy as soon as I could. The very poor sharpness on just the right hand side when close to the 70mm setting jumped out at me - careful tests simply confirmed how bad it was. It got better away from 70mm, but this performance made my old 40 EF80-200 f4.5-5.6 look stellar! (I've had decent A3 prints from it.)
I requested a 2nd. copy and although (now knowing where to look!) I can still see some problems with this copy, I decided that the performance was acceptable, and nearly a year on that was the right decision.
It covers a useful range on my 5D, focuses fast and pulls in detail in urban landscapes extremely well. It's light enough to live in my bag (I guess the f2.8 version would have lived at home.), and I'd recommend it.
Standard of Build? Similar to my other L lenses - feels solid, but so does my EF 85 f1.8.
Do I use it for birding? Not intentionally. I use my EF300 f2.8L IS with extenders for that.
My low rating is simply that I object very strongly to doing Canon's QA on an L lens, or on any product. (This is only my 2nd.lens purchased new - my copy of the EF 100 f2.8 macro USM also needed early repair under warranty as it started coming apart.)