Often, as I read the external letters of evaluation written by experts in support of the tenure cases of stellar junior faculty, I wish these young professors knew how highly the senior colleagues thought of their work. Some of these letters are full of genuine praise and admiration.
If you are an academic, it’s likely that you sometimes — perhaps often? — fell insecure about your professional standing. How could you not? Everyone around you is smart and successful, and the competition for funds and top publications is fierce. There is very little, if any, direct affirmation; you only ever get it indirectly through accepted papers, citations, invitations to give talks, or an occasional award. I bet it would feel really good to read, black on white, how much your professional peers and elders admire and respect you.
xykademiqz 
Yes. A couple of years ago I applied for a job in Scandinavia, which had an open procedure requiring the applicant to submit support letters from three referees (professors from three external universities), instead of the referees being contacted directly. This meant I could read what the referees wrote about me and one of the letters in particular brought me to tears, as the writer had such a high opinion of everything that I do. I will never forget that feeling and I will be always grateful to that writer.
There is often a disconnect between written praise and oral badmouthing, however. I’ve seen plenty of cases where someone writes glowing praise of a colleague, but then when you talk to them in person, perhaps after they’ve consumed a drink or two, it’s completely the opposite story- how much a worthless ***hole that colleague is.
As one of the commenters said above, though, I often feel that what is written in these letters is not genuine. Unfortunately, the current culture in the US is that any recommendation letter you write is expected to be utterly glowing–the “walk on water” type of letter, as we refer to it in our lab. If it is anything less, the candidate will be looked at unfavorably. Recommenders know this, and thus (if they have good intentions) usually do their best to make their letters the “walk on water” type, even if they don’t really mean it. So I am not sure I would get much out of reading a letter full of such glowing praise for my work, because (a) I know that the recommender would likely write the same or similar things for anyone else asking for a rec letter, and (b) I would attribute more of what s/he writes to “expectations of what a rec letter should look like” than “what s/he actually thinks of my work.”
Sorry to be a downer, but that’s my take on these things…
In many cases, the letter writer asks to provide a draft. I have written 5 drafts this week for my proposal this week. In some cases, letter writer added their bit, and in some cases just the letter head and signature.still it is nice if someone writes glowing letter for you. I wish I can collect all those for my own sanity 🙂
I agree that often what is written is not genuine, but that’s not to say these letters are never true or never genuine. I think it’s not hard to tell whether a person has written a specific, detailed, strong letter versus a generic superlative dump. My point was more along the lines that I wish people, especially junior ones, could see some of the genuinely nice and supportive things that people say about their work.
Not sure how universal this is, but when I went through tenure last year, I received copies of the support letters written at each stage (department, chair, college, dean, provost). The departmental letter quoted heavily from external letters (with names redacted in the version I received), and that was incredibly gratifying and a very positive experience in the midst of a process designed to be stressful.
One of the problems with this trend in my field of having to write my own letters is that I never get that nice validation. I ask my mentor for feedback – and she just says that I am doing a great job. I feel like I am being needy when I desperately want to ask exactly what I am doing well. I want that both for the validation, but also so I have a sense as to what I am doing well and what I need to work on for success along my trajectory (am a postdoc, btw). Critical feedback tends to come only when she is worn out and cranky – and that isn’t super helpful either because it is more about where she is than that I am doing something that needs to be improved.
It would also make it easier to write my own darned letters of rec. I also keep fervently hoping that when I send my mentor a draft of my LOR, she will add the stuff she thinks but doesn’t say – but she doesn’t.