I was one of the early Elemental purchasers that got FE and LH comped. After the initial WoM launch I hadn't actually played until about a week ago when I decided to give LH a try. I am much happier with this - if this had been what was in the box when I originally bought WoM I would have been satisfied with my purchase.

That said, I have encountered a lot of bugs. Most are minor to moderate, but all are significant enough to mention. I started taking notes while I played and here are what I have written down.

Plain bugs:

1) Strategic map pathfinding estimates (the numbers on the route of what turn you will arrive where) are sometimes off by one tile. If you move the cursor away and back again it will usually be correct. This tends to happen a lot when I have several armies with different movements. I suspect it may not be properly updating when focus changes after moving an army with a different movement.

2) Tactical map tile picking can sometimes be inaccurate, especially in larger maps that have a lot of vertical slope. There is little more frustrating than clicking what should position a heavy-hitter perfectly and watching it move one tile away from where you had clicked. This would be much more visible (and easier to work around) if the tile you are hovering over would visibly highlight, making the final location clear before you click.

3) Tactical spells that select a random target (such as storm) seem to select independently for the effect and the VFX. They almost always show the explosion/spark/etc. on one unit while a second unit gets the floating text and damage.

Exploitable balance issues:

4) Upgrading unit size only costs cash, regardless of materials required by the unit. This means it is significantly cheaper to build 3-strong units of material-heavy (horses, crystal, etc.) units and pay a tiny bit of gildar to bring them to size 6. Upgrading weapon or armor correctly costs materials to avoid this, but this trick effectively doubles your horses/crystal/wargs for what is a trivial amount of gildar by the time you are building 6-strong units.

UI issues:

5) Fog of war does not reveal as an army moves, only at the end. You can work around this by moving one square at a time, but it is an annoyance. Particularly in early to mid-game when you have a lot of roads (so even a basic army may move 8 tiles at once) but still some unexplored territory near them, this is a big deal.

6) Strategic map autoselect-next-army happens when the moving army finishes its turn, even if you have manually selected another army while it is still moving (very common when a 4-5 movement army is walking a long distance along roads). This can cause an order intended for one unit to go to another. Example: Send army A on very long move order. Click army B. Right-click where you want army B to move, but a split-second before you click army A finishes its movement and autoselect-next-army has selected army C. The click sends army C to where you wanted to send army B, at best wasting a turn and at worst doing something foolish. 

7) After defeating an elemental lord, you get a one-time-only chance to select a city for its bonus item. However, you don't get to look at your cities or scroll the map when deciding - all you get is hovertips giving the production/research/etc. of your cities. If you've memorized everything about your cities this would be no big deal, but I remember which city is which more by location than by name and don't always remember the name of the city I'd want to use.

8) The popup when gaining a piece of loot only offers the option to equip it then and there or cancel, without letting you view its stats or the champion's current equipment. This would just be a UI annoyance, but if it is at the start of the turn and you are about to be attacked by another army it's a strategic decision you don't have the full information to make unless you wrote down all the stats last turn.

9) A unit with no abilities off cooldown and nobody in will automatically pass after moving. The trouble with this is that if you aren't paying complete attention and forgot impale was on cooldown, it's very easy to move a spearman, click pass intending for him to pass, but instead cause the next unit (instantly auto-selected) to pass. For consistency it would seem easier to never force a pass. It doesn't force a pass when a unit is webbed and has nothing in range (another case where passing is your only option) so it wouldn't create inconsistency. I imagine auto-pass was more useful when weapons didn't provide active skills.

10) Speeding up tactical battle speed also speeds up tactical edge-of-window scroll speed. At 5x even grazing the edge pushes you all the way to the edge of the battlefield, causing an annoyance.