I have both the Lelya 2.0 and the Leshiy; no complaints about either. I bought the Lelya used here a month ago- it's been a hammer and absolutely amazing. Incredibly easy to shoot offhand (the only way I shoot) and my girlfriend is Annie-freakin'-Oakley with it. The Leshiy... is in a class by itself. Sure, only single-shot.
Nothing beats it in the woods for hunting small game. I can go from .177 and low-power to big-bore critter-bashing in minutes, literally. I've spent some time documenting settings and power levels with my .22 shorty and lojng barrels, have a 350mm .25 barrel on the way, and a .177 400mm barrel will be coming eventually.
There's no doubt the BP-17 is an awesome little pop-gun. I'm contemplating them hard, but the Lelya shoulders extremely well, it has dual-cocking, and ergonomics in general are superlative. I love the simple magazine design... And still prefer shooting my Leshiy more. For traipsing in the woods (or canoeing) there's literally no other PCP I'd prefer having with me.
Regarding the Leshiy in particular: these are not novelty airguns. They are simple, high-quality, robust, and accurate hunting/pesting tools that are as close to perfect as I could ask. Are they niche guns? Well, if your niche is sitting at a bench or table and pesting at 80+ yards, or perhaps if you are competing in EBR or similar, the Leshiy is not in your "niche". For getting out and actually carrying an airgun afield, there's nothing I own that I consider as enjoyable, durable, and easy to shoot accurately anywhere, except perhaps my Blue Streak.