In looking back at ICHEP, what are my personal overall impressions? The conference was very well organised (with the minor exception of the dinner), the venue was great (as were the conference bag and its contents), the President felt obliged to attend -- so it was clearly a good and successful conference overall.
It was also pretty big (for a physics conference, not in the greater scheme of such things), in fact almost too big for my taste; perhaps it's just that as a theorist I'm naturally more introverted, but I find it difficult to meet people and start a conversation when there's a huge crowd. Smaller more focussed conferences are probably better for discussions; there was also a notable lack of questions in the plenary talks -- perhaps also a symptom of excessive size.
On the other hand, the huge size means a very diverse set of speakers, which enables one to learn about all the things that have recently gone on in the wider field. Since the arXiv is getting so vast that it is well-nigh impossible to even read the titles of all papers that get posted to the hep-* sections (much less the abstracts, to say nothing of the papers -- even assuming that one had the exceptionally broad knowledge base to be able to make sense of all of them), this overview is perhaps the most important function of a large conference like ICHEP.
And the things to be learnt were of great interest: CMS and ATLAS have "rediscovered" the Standard Model; that in itself is no surprise, but the speed at which the LHC experiments have managed to get there is amazing at least for this theorist. The arrival of the LHC hasn't rung the death-knell for the Tevatron quite yet, though: while rumours of a Higgs discovery turned out to have no foundation in fact (a 2σ deviation is hardly a basis even for a rumour), CDF and D0 combined could exclude a much larger mass region for the Higgs, further narrowing down the regions where it can hide. Also from the Tevatron comes the like-sign dimuon charge asymmetry that may be the first sign of new physics if it is confirmed by another experiment. Away from the big colliders, the neutrino physicists and cosmologists are also doing impressive work and chipping away at the Standard Model's plinth. The representation of my own field of research was perhaps not optimally suited to the audience, since the parallel sessions on lattice QCD were not very well-attended except by the lattice people and the plenary talk concentrated on work that would likely have enraptured a nuclear physics audience, but probably not a HEP one. Overall, I got the impression that the experimentalists take ICHEP much more serious as a forum than we theorists do -- there were a lot of new experimental results presented for the first time at ICHEP, whereas most of the theoretical results had been presented at other conferences or been posted on the arXiv earlier.
Blogging a conference as part of a group rather than on my own blog was an interesting new experience; for a lone blogger, ICHEP would have been way too big!