Absolutely. Anything you can learn to make you a better, safer pilot is always worth it! How can you put a price on that? Not to mention, the emergency procedures you could practice that would be inadvisable in a training aircraft. The military and the airlines have been using simulators for years to throw every possible scenario, as well as practice procedures. That's good enough for me!
Speaking as a 220-hour private pilot who is working on my instrument rating - I'm currently using a PC-based flight simulator and my time is completely un-loggable. I'm fine with that. I am able to practice all the things I'm reading about in my self-directed ground schooling, ingraining many necessary basic skills before I even set foot in the airplane. That makes my time in the airplane much more productive.
I got my PPL back in summer 2000 @ ROC and got about half-way through my instrument work in the 6 months that followed (I was young and poor back then - now I'm much older and not quite as poor). I stopped when the tech bubble started to burst and my economic situation became somewhat uncertain. For various reasons I didn't really get back into flying again until late 2014, now in the NW Georgia. I finished a comprehensive BFR in January 2015 and in the last year have packed on a good hundred hours of experience, including my tailwheel.
With all that new confidence available to me, late last year I had the bright idea to pick up where I left off in 2001 and knock out my instrument rating. I quickly found out that the 20+ hours of simulated and actual that I logged 15 years prior was completely and irredeemably out of date.
So - fall back, regroup, new plan. I've spent the last few weeks working on my general knowledge in preparation for the written. Since I have more than half of my instrument time logged already (about 24 hours), I'd really like to wrap up as close to the legal minimum as possible to keep costs under control. But I DO NOT want to compromise safe operation, nor my abilities.
My solution - home sim practice. Look at all the things I can do while not being billed for the airplane or CFI -
Getting my scans down, including what instruments are primary for a given maneuver and flight regime - check.
Tracking, intercepts, holds using different fixes and equipment, full approaches, and putting all the pieces together - check.
How to properly use the Garmin 430W that's in my real airplane, including flight plans, procedures, editing waypoints en-route, etc - check.
Training to use with ADF (and even an HSI) even though my training airplane just has VORs and GPS - who knows what I might fly in the future - check. Oh, and I could also get a nearly fully functional G1000 IF I ever found myself wanting to fly a glass 172 or 182 (though not likely). DOUBLE-check. If course, were I to go that route I would do so in conjunction with Max Trescott's G1000 book. But frankly I'm a low-winger at heart.
Full control over weather so I can make sure I'm in the soup down to minimums, changing winds aloft, and turbulence to force me to identify and correct nascent deviations - check.
CRM - figure out the right mental and finger-tip workflows to manage my charts and other references (foreflight) in the various phases of flight - check.
If and when I feel ready to do so, there are even high-quality "live" ATC products available for me to use while flying in the sim (e.g. PilotEdge) so I can improve my comms skills. I'm not there yet, though - one new thing at a time.
So I may not be able to log the time, but I bet practicing on the home sim will save me 20 hours in the airplane and a LOT of frustration without compromising my capabilities nor safety long term. I'd venture I'll be a better instrument pilot when all is said and done, for a given quanta of training hours in the airplane.
Full disclosure - I already had a powerful PC and decent control hardware from years past - yoke, throttle quadrant, pedals, etc - and I made a significant investment in software ($200 for Prepar3d V.3, $250 for high quality aircraft, GPS, and navdata add-ons). But if that $450 saves me 15 hours in the plane that's >$2500K in savings ($200/hr fully loaded for AG5B/CFI/tax + incremental ground time). Plus I get to keep practicing for free after I get my rating. I think that will be very important in the first few years after I receive my next "license to learn".
Onward and upward!