Considering their price, as you say "cheap", apparent quality, good(I say apparent as I'm no expert), I'm amazed at myself at never having owned a Radio Shack Sound Level Meter. Even if no terribly accurate measurements can be done it's still a pretty cool gadget and I am a "sound person"(Always, and I mean as long as I can remember, interested in sound.) and it's the only tool around for measuring at least it's level that I could buy almost anywhere I've lived, for a relative "nothing" price - and they've been around for a long time. No, not so amazing as embarassing that I never had one.
I do now. And, at least to look at and begin to use, it's even "cooler" than it used to be(Though no analog version anymore. For quite awhile you could get either digital or analog.).
The final reason I finally drove the mile down the road(Could've walked, I need the excercise) and forked over the cash is the 'Real Traps' web site, which offers "a plan" for it's use. A highly sophistocated, incredibly accurate means of determining all the accoustic problems of my studio? I suppose not. But, it is a great excuse to finally buy one of the gadgets I'd thought about for many years and the RT plan(With tones you can download for the purpose) may be a nice indicator of how my room "works", or at least SOME indicator, other than my ears - and while I've only put about 20 minutes into the "room measuring project" so far, I can say that up to now my room looks(On the meter) pretty bad...... I'm not surprised, but, it is kind've neat-o to actually "see it", even if only sort've, to some degree - picture worth a thousand words(Which I don't entirely agree with - I'm a word person.) and that sort of thing.
In the end it's just a "volume meter" you can carry around with you(Hard to carry around all(Or afford) the gear, seperately, even if you DO have it - an old cassette machine with built-in mic and a tiny VU meter could do much the same thing if you can turn it's horrible ALC off.) and I'll bet it's as accurate as most volume meters we DO use and blindly trust.). YES, buy one, use it when you can for what you can, otherwise, stick it on a prominant shelf and let everyone else who has long wished they'd bought one see that you did - "Hey, this must be a 'real' sound guy!". Do your basic tests with it THEN, if you even can, hire a pro with the "real" gear - or not... Or, just assume your untreated, unplanned room IS horrible(It is!) and start 'treating'......
TG