I think that they're worthwhile. I've got a $50 one from Woodline/Japan Woodworker, and it's worked well. It's a small backsaw which works brilliantly for fret slots and does a good job of smooth trimming.
Sorry, I meant the professional grade ones, like the 240mm Professional Grade Dozuki Saw Kondo
Nagaoke 210mm Professional Grade Double Edge Saw (Ryoba Noko Giri)
There a lot of money, but are they worth it?
I work at a place that sells these, various different ones including the Japan WW stuff, Robert Larson's and some very cool pull saws made by Vaughan (if you're a carpenter you know these guys - they make great hammers). Since we have a shop also - we get to play with most of what we sell. I find that price has little to do with quality in these tools (except when you get into the REALLY expensive ones (over $100), which are very nice, but not necessarily better than a moderate priced saw that you've carefully selected). My favorites (your mileage may vary):
Western style lumber saw with japanese style teeth (this for example) - gets used maybe 5 or 6 times a year but it's always like short, hot love affair. Great for knocking together parts for your new bench, hacking off some plywood, making a clean cut at some crazy angle that no table saw can handle. Looks like a crude tool but find a short stiff model and you'll treasure it. OK, so you probably don't want to use this on an instrument :) Ours is a Disston (not an antique - some newfangled company, I can't find it on the web) about 28" long and 8 TPI and it's real good fun.
Cheap dozuki ( like this ) - get a cheap one and use it all the time! Don't waste money on the Camelia oil for rust prevention, but don't leave it in the rain either, they suck when rusty :(
For a back saw, I like a good old fashioned Sheffield steel fret saw, but knock out the blade and reverse it so it cuts on the pull. Larson has several 'Gentlemans Saws' that are OK for this, but I find that teeth set by bending rarely give the precision of a japanese tooth. Oh, and don't buy an .028 kerf saw and sand it down to .023 for fretting - pay the money for the proper .023 saw.
For fine work, much as I like the aesthetics of the japanese made tools, these two are my favorites (and they are low priced):
Vaughan flush cut - this is a very flexible blade, but if you make a quick jig for your cut (think instant mitre box) - it makes a very fine, clean, very narrow kerf, easy to control cut. That thread about the strat nut makes me think of this tool.
Then, of course there is the scary sharp violin makers knife, which, if you have a good one, you're probably using it instead of a fine saw. And also the XACTO saw which you know and love. OK, now I've gotten all hot and bothered, I'll shut up for a bit :)
I use an Exacto saw and just for a little extra control I rubbed down the teeth on the end so for a few ( 15) mms it changes from smooth edge to saw teeth .You can get it right on the line that way .I put a plywood handle on it too so my knuckles are tucked away when cutting really close.
Go to Harbor Freight and find a Japan saw. Keep looking and get a fine tooth one and by a couple as the steel is very hard and some times when you hit a nail or truss rod it will take off several teeth. I also have a small Japan flush trim saw that is very nice. I only use these in my guitar work.
Wow you guys make me drewl, I think I could write a book on how to be a competent luthier using only cheap tools , and often the wrong way.But I dont think some of the big suppliers would like me .I'm just gona shut up and wish I had some of that great gear.Len