Last spring I ordered a pair of mouthguards from Darren Macdonald at Smartguards.ca, I've been wearing them for all my goalie and skater sessions since then. My cost was $120 for a single guard or $180 for two (any design included, though I chose boring ones). This price is including a DIY kit for the mouth mold (no dentist visit required). It's less if you're in Toronto or have your dentist send him a poured-in-stone impression. Subsequent orders will be cheaper as he keeps the mouth impression (I'm not sure why I'd need to do this other than to get different designs).

Rating
Mouthguard:
Fit: 10/10
Comfort: 10/10
Breathing: 10/10
Speech: 7/10 (without mouthguard is 10/10)
Appearance/Customizability: 10/10
Durability: 10/10
Cleaning: 10/10

Smartguards.ca
Custom Fit DIY Procedure: 8/10
Customer Service: 8/10
Overall: 10/10

Summary First
There's simply nothing I would change about this mouthguard. They're perfect, they do the job they are supposed to do, and while wearing it, I completely forget it's there. They are much, *much* less annoying than the boil-n-bite mouthguards I've tried (I've had a fair number of those, even the supposedly 'better breathing' ones).

Technology
These mouth-guards are double-layer pressure laminated. They are the top-end mouthguard you can get. This is the same quality mouthguard that your dentist will offer you (unless your dentist is only offering the poorer-quality 'vacuum formed'), they're the same type the pros wear.

Darren will offer you a thicker laminate if you want, but that's really only needed for boxers, MMA fighters, etc. For hockey players, it's probably overkill. Talk to him and he will put you in the right protection based on your particular needs and wants.

Speech
Speech is not perfect, but that's just what you get when you wear a mouthguard. I can speak a lot better than with any of the boil-n-bite mouthguards I've tried. You can be easily understood when speaking with this in, although you do have a bit of a lisp.

Playing with the Smartguard
As I mentioned above, playing with the guard is great. I really don't notice it's there after I put it in. I sometimes practice without it and there's no difference with breathing. My nose is almost always blocked up partially or wholly, so I'm a mouth-breather (insert jokes here).

Though, the first time I played with it in, I found that I was chewing on the guard pretty good. Not because it was annoying, but just because. It was kind of like chewing on gum actually, it probably triggers some sort of innate oral fixation. The first game, I was really going to town on it, and the next day my jaw was aching. It was really killing me! I was a little worried that was due to the guard, but I suspected that it was because I was really gnawing on the thing. Subsequent games I kept my chewing on it to a more reasonable level and there has been no discomfort at all.

I still chew on it a bit during games, but again, it's just because it feels natural to do so. I kind of like it. And apparently, that's one of the ways that mouthguards protect from concussions, you're more likely to have your muscles activated, which helps prevent the whiplash effect.

Even after all this gnawing, the guard is still in perfect condition. There's a tiny bit of dent-like tooth marks on the bottom side of the mouthguard, but absolutely no structural issues, no scuffing, cutting, tearing etc. I don't think you can damage this thing unless you skate over it.

Protection
I can't speak much to this, fortunately. *knock wood* You can read all about double-layer laminate mouthguards and their protection against mouth injuries and concussions.

I wanted to order a good mouthguard as I'd been getting jostled a bit, and often had my mouth open. Especially bad was when I'd get lateral hits to the head when looking behind the red-line. Sure my leagues give 4-minute penalties to the slightest stick infraction, but they don't seem to care about guys dishing out blind-side hits to the goalie's head.

I took a pretty hard hit to the side of the head two games ago when a duffer couldn't stop after I'd made the save and tracked the puck into the corner, and it didn't phase me too much (though I did very clearly explain to the meathead why skating that hard to the net if he can't stop is a very bad idea. Especially when there's under 30s left in the game that they are leading 8-3!).

Last game, I took a full-on Luongo chin-shot that popped off the bottom clips on my mask. It was a hard slapper right from the face-off dot (beer league rink size). It packed a hell of a wallop but it barely phased me. My wife was taking pics and you can see that I'd picked up the puck before it even hit the ice (please hold all applause until the end of the review). Had my jaw not been clenched, or had I not been wearing a mouth-guard, I think it would have been ugly.