Alright, I beat the game with a clear time of 8:18 including a decent bit of grinding in the later stages.
It really is a great game from start to finish. There's a good amount of enemy variety and the boss patterns are really fun for the most part. The length is perfect for what it is (its pretty tough to do more than 1-2 stages in 1 day because it's really tiring on your arm with all the non-stop slashing). There is a good amount of secret things to do after the game too.
For instance, there's an area where you can fight 4 super boss battles and if you beat them all I guess the ultimate super boss. The only thing is that each boss requires a certain amount of rank experience to fight them (you get rank points after you finish a stage and you advance through the ranks which give you new abilities like "x" spell lasts 2x as long"). After finishing the game I had enough rank to fight the first two and after finish them I had enough to fight the 3rd, but I don't have enough rank to fight the 4th one.
Also in the stages the path splits a few times and there are rocks blocking a direction. You can exchange medals for items that break the rocks and explore new sections of the stage to get rare treasures.
Then for the dedicated people, or those with no other games to play, you can try to make the best sword. To do this you have to grind SO MUCH to get the money and the rare items because the best swords require you to make the 2nd/3rd/4th best swords and combine them to get it. If the game takes 6-10 hours to play, grinding for this would probably add another 10 hours and double the game length for those who enjoy 10 hours of grinding.
Overall:
+Good control scheme
+Super attacks are fun
+Rpg aspects like equipment, money, exp are good
+DQ nostalgia and presence is great. Seeing rare metal slimes fly across the screen, knights jump on slimes and ride them out, treasure chests try to eat you; it's all nice.
+Boss fights are awesome
+Stages and their branching paths are good
+Graphics and music are good
+Voice acting is good
+Buddy system is good but the prince kid is useless
+Length is just about right
+Substantial amount of post-game fun
-There are a few attacks that require far too high of precision for Wiimote controls. Normally the controls are good because the game doesn't penalize you for not being exact, but towards the later stages it sucks taking heavy damage because the Wiimote read your input incorrectly. For example, some attacks you can't just defend because they attack at 2 or 3 points across the screen at an angle. Because of this you have to do a single slash in exactly the perfect angle at the right time to deflect them/destroy them. But you might do a horizontal slash and the game reads it as a slightly tilted horizontal slash and it appears as an angle on-screen and you get hit.
-These leads to the idea that the game really should have checkpoints/save points in dungeons, at least before bosses. I know it'd be very "un-" DQ to do that, but if an attack doesn't react correctly and you die 30 mins into a stage and have to redo the entire thing again along with all the exact same battles again...it'd be frustrating. I made it through ok, but I got lucky at a few spots which could've ticked me off pretty bad if I had been 'unlucky" and had to redo stages.
-Some enemies just aren't that fun. It's only a handful, but some you have to just sit, sit, sit and block until they finally open up for attack and then if your sword isn't strong enough you sit, sit, sit and block until they open up again. Normally enemies should be fast and have lots of opening so you can blow through them.
-The rpg aspects like grinding (forced by the game setting money costs so high on some things or by require tons of rare items) could have been left out.
-Moving in towns could be better.
It's a great game and I'd definitely put it up there with Zelda/FE as the must-have Wii games.