I think author misused GTD. GTD allows me to dedicate uninterrupted time for "deep work" precisely because I know that there is dedicated time and place for dealing with "shallow" work and it's take out of the way. Allen himself writes about not being to do everything, for me it means that there should be conscious effort to limit amount of "shallow work" you do and may be decide not to do some items at all. In other word if all you time goes to "shallow work", then you prioritized your projects wrong.

Also, GTD book is one of the most badly written books, the style is watery, and just hard to get through. It could be compressed threefold without the loss of meaning. I opted out for audio version which I could listen to on faster speed. This is a pity that invaluable advise comes in such package, recently I started to re-read, but now thinking about trying to reading some of this "GTD Summary" books instead. I wish somebody would buy license from Allen to rewrite it in digestible, concise way.

Also, I was using (and paying for) RTM for years for my list keeping, but it's just not optimized for GTD and web UI needs long-required update. Nirvana HQ finally got smartphone client, I switched to it and it's really good. Nirvana's web UI is well structured, compared to RTM it needs better keyboard shortcuts and group operations, but overall it's much easier to use for GTD than RTM.