I've got a plain 'ole Whisper (well, I suppose plain isn't quite fair; it's got a GRT-3, gas ram, wood stock, and 4-16x40AO mil-dot scope) in .177.
It has settled in QUITE nicely after I installed my gas ram and did a tune at the same time. 9 months later and several thousand pellets through her, and I haven't lost any FPS. With JSB exact heavies, I can take a tree rat in the head RELIABLY out to 35 yards, and get 'em with a heart/lung shot out as far as 58 yards (in fact I got one this past weekend at this range).
I had some side-to-side barrel play issues awhile back, but I've found that so long as I keep the breach seal in good shape (replace frequently; I've put in three new ones in this timeframe with the shooting I've done) the Whisper remains very accurate.
Take care of her, and I'm sure you'll enjoy her for years to come!!!