Precise observations by a couple folks here have found that the Spring Drive tends to run quite a bit more accurately than the stated +/- 15 sec/mo - closer to 0.15 - 0.20 seconds per day - around 6 sec/mo or less.I'm sitting here 36 hours after setting it (my new Snowflake) and cannot see any drift, which is expected. Further, knowing the watch is insensitive to position, temperature, the tide being in or out, etc. means there is no 'luck' to just happening to keep it in the right position overnight or at the right level of wind (other than dead!). In a week, a month from now, I should start to understand what I have. I know it is rated at +/-15 seconds/month and interested to see how mine fits into that.
I will answer you in somewhat the same vein as your question was asked - partly seriously and partly in jest. Owning and wearing a Grand Seiko Spring Drive has ruined wearing any other watch for me. Now here I say "ruined" somewhat in jest because I still very much love wearing my other watches. But I don't think the experience of wearing anything else compares to the experience of wearing a Grand Seiko Spring Drive. But not necessarily for the accuracy, though that is a nice bonus.I ask this question partly seriously, partly in jest, but still curious as to your take. Does using a Spring Drive, which you might need to set monthly, ruin regular mechanical watches in terms of their accuracy and potential fussiness (for example, having different deviations depending on the state of wind, what position they are left in, etc.)?
If you have a rather large collection of watches, and tend not to wear the same watch day in and day out, and therefore let your mech watches "run down" between wearings, then accuracy really doesn't matter so much as long as the "per day" +/- rate isn't insane. I abandoned my watch winders as a bad idea some time ago. If the watch isn't being worn it doesn't get wound. So the watches tend not to run long enough for the accumulated deviation to matter. They'll need to be re-set each time I wear them anyway.
Even though (somewhat ironically) they had to use electronics to help pull it off, for me it is an incomparable experience to wear the world's only current-production watch that is truly analog (no counts or beats or steps) with a flawlessly smooth seconds sweep that is actually continuous. The watch does not keep time like a marching soldier, step, step, step, but more like a spinning planet. For me there is something amazingly serene about that. Not just how it looks (because a couple other watches simulate the effect and have a seconds-sweep that looks similar) but in knowing what the glide wheel is doing, seeing that flawless sweep, and knowing that no matter how much you slow it down, there are no steps.
Add to that the fact that this wonderful little machine is installed in an exquisitely finished case, dial, hands, etc. And also add to that the fact that I'll probably never see another one on anybody else's wrist in my lifetime (unless perhaps I'm in a GS dealer's store - and I've not even seen anybody actually wearing one there either so far).
While I don't think I'd be nearly so enchanted if it was less accurate than a 100% mech, the fact that it's more accurate than a 100% mech is honestly the least wondrous thing about it for me - just another bonus.
All of that said, I still love my 100% mech watches, and I wear them more than the GS SD. I tend to wear the GS SD either when dressing up a bit, or on days when my mood could use a little pick-me-up and the reflexive smile I get from a brief stare at the marvel on left wrist makes a difference. The exquisitely polished case could easily be damaged and if that happened I know I wouldn't be happy until I sent it back to Japan to be re-polished, so it's not my daily driver. Some day maybe I'll own a "beater" Spring Drive for daily wear?
At heart I am a "100% mechanical" kind of guy, but the SD gets a pass for what they've achieved despite "polluting the mech with the tech".
Enjoy your new watch. Welcome to the Spring Drive club.