Okay, in no particular order, here are the bugs as I found them. These are all from version 0.5.0, using Windows 10. (I know it's a longish list, but that's because I'm a bit of a perfectionist; DiabloRL is great, I swear!) :D
Magical items should appear blue in your inventory. (Likewise, unique items should appear yellow) They appear as their proper colours when on the ground or in shops or when you're wearing them, but if they're in your main inventory, everything appears grey. (Can probably also apply to potions and scrolls as they appear in your belt too)
Normally, if you can't wear or wield an item due to a stat being too low, the required stat appears red in the description of the item, but if the item is unidentified, it seems that a random stat appears red, even if you already have that level of stat. For example, an item required strength of 17 and I had strength 20, but when I looked at the (unidentified) item, the "Strength 17" appeared in red; if anything, probably the word "unidentified" should be red instead.
Every time you buy a premium item in Griswold's shop, it reshuffles his inventory and he has a completely different set of items for sale. I don't think this is intended.
Using Fast Travel often bumps into and goes down the stairs you just came out of. It could probably use a tweak in the path-finding to go around stairs that are right next to you. (BTW, love the Fast Travel system; it's a great feature) :)
Inventory immediately closes when you put on or wield anything. (Though not when you unready them, interestingly) Similarly, the belt closes when you drop an item from it or transfer an item from the belt to the inventory. (Though not from inventory to belt, interestingly) I think they should remain open until you close them, regardless; I'm pretty sure that's how it worked in Diablo too.
Archer type enemies continue firing at you, even if they can't see you, even if you're out of sight radius of each other. You can see the arrows they fire flash on the screen, even when they're on the other side of walls!
Using the look command to look at unique quest enemies that you can talk to (such as Gharbad and Snotspill) doesn't work. After the quest has run its course and you can fight them, the look command works properly, but you should be able to look at them before talking to them.
Is Shadowdrinker (unique zombie) undead? I tried firing holy bolts at him and they didn't seem to do any damage!
Minor typos: In Adria's text for the Arkaine's Valor quest, should be "the" instead of "they" and in Ogden's text, the audio contains the phrase "the warrior," but that phrase is not in the text.
Murky Pools do nothing. According to the Diablo wiki, they're supposed to cast the Infravision spell.
For Secluded Shrines, (which map out the level) it would be nice if there was some way to distinguish which areas I have been to and which are unexplored. (Perhaps, it could map the walls, but not the floor?) As it is, it makes exploration very difficult, because I have no idea where I've been!
If you're wielding a weapon that confers knockback, the knockback applies to spells you use as well. (Such as Firebolt) This shouldn't be. It's supposed to be just hitting with the weapon that knocks enemies back.
Typo in the mortem text: "hypohondriac" should be "hypochondriac." (I'm assuming this description applies to characters who overuse Pepin's healing ability)
Typo when you use mana potions: "Megical" should be "magical."
Infravision doesn't reveal hidden or cloaked enemies. It should. In the original Diablo, that spell is a way of finding those guys.
When using ranged weapons, you can't manually target enemies at the edge of your range. (Though if you push TAB to cycle through enemies, it targets them properly)
It doesn't seem to be possible to assign Quickskills, (hotkeys) or at least, if there's a way to do it, I can't figure it out. I should be able to use F5 to F8 to choose pre-selected spells, rather than having to switch them manually every time.
You can't always shoot enemies you have line of sight with. Like you can see them, but your shot tries to fly in a straight line and hits obstacles between you. I imagine this would be difficult to correct, although maybe you can just borrow the algorithm from DRL? :)
That's all for now. I'm sure some of these are easier to fix than others, but they're pretty much all minor things. If I come up with any more, I'll share them here. :)