I am, IMHO, a very good solver, and I had never, even once considered things like white space, word count, etc. until I joined this list. While the information being discussed is EXTREMELY interesting, I don't think it will ever change the enjoyment I get out of a particular puzzle.
I have constructed 3 puzzles in my whole life, and if I was as good at solving as I am at constructing, well, trust me Dell's Easy puzzles would probably be over my head. I think I can speak almost exclusively from a solver's viewpoint.
What things (to me) make a good puzzle?
1) Overall enjoyment. I realize that this can't be quantified, but to me it means a puzzle that is suitably challenging, that I can complete without references, and that has a certain "flow" to it, i.e. the puzzle just goes along,and, all of a sudden, you're done, without really even realizing it.
2) Trying to define "suitably challenging": To me that is a matter of perspective, or mind set. In the NYT the mind set is obviously different from day to day. Unlike some, Monday puzzles don't bother me. I think the "game" needs to draw in more newcomers. If I sit down with someone and go over a Monday puzzle clue by clue, they end up saying, "Yeah, I could do this" (even if, in reality, they couldn't). If the puzzle is interesting, has a fun/interesting theme, then it's enjoyable. Difficulty level is not the sole determinant. There have been Saturday puzzles that disappointed me by being too easy. Again, it's mind set. Put that same puzzle on another day, and I might say "Whoa, this is way too hard for a _______"
3) Informative. I think most people who really like crosswords, also like to learn. I know I do. If I learn a word that I can add to my vocabulary, I am ecstatic. If however the answers are things that I have no other reason to know or care about, I feel differently. If they are "crossword answers" like Arne, Agee, Aral, Ural, Enid, Etna, etc., I will begrudgingly commit them to memory. If however, they serve no other purpose than to, IMO, artificially make the puzzle more difficult, than I have no use for them. A puzzle like last Saturday's containing (to me) who cares answers like URSO, DUPRE, DEREN, et al. is not enjoyable. When I completed last Saturday's puzzle my feeling was not "That was fun", but rather, "I'm glad that's over." Why not skip it? Matter of principle. I "have" to complete the puzzle every day.
4) I don't like foreign words. Admittedly, I may not be in the majority here. I know that Spanish words, in which I am fairly literate, don't bother me anywhere near as much as French words do.
5) Partials and phrases don't bother me as long as they make sense to me. This is almost never a problem. One recent exception was Sunday's "___________cost to you". I assumed the answer was ATNO until I saw five letters. ATONE was/is not familiar to me. I could understand it better, I guess, if there was no other way to clue it. However, in this case, there are dozens of alternative clues.
6) Abbreviations. This is one area where my opinion has been changed by being on this list. I used to HATE all abbreviations, usually because they were clued New Deal Org. or the like, and I had no idea what it was even after I finished the puzzle. Now I know that constructors hate them too, and use them only as a last resort. Therefore my tolerance level has increased.
7)Themes. Somewhat ambiguous here. On the early week puzzles, I'm usually done with the puzzle before I even consider what the theme may have been. Theme/No theme - doesn't matter to me in the weekday puzzles. Sunday, though, that's a different story. The more clever and innovative the theme is, the more I enjoy the puzzle. Maybe the most satisfying answer of the whole week is the answer I write in immediately after "getting" the catch or gimmick or theme. It may take just a couple of minutes, or sometimes I have to solve quite a bit of the puzzle first, but once I catch on, the rest of the puzzle just rolls. Solving a good Sunday NYT puzzle is my most satisfying crossword accomplishment.
Well, I have certainly rambled on here long enough. Sorry about that. Just trying to present the solver's side of the equation. If something I've said doesn't make sense, or I've not addressed something, please let me know, and I will try to give a less verbose response.