PS: GREAT GAME SO FAR.
1: The experience system isn't the best, each level you need just slightly more experience (less than 10) than the previous level, yet as you get higher level things give more experience. Some test numbers that aren't based on truth:
Level 0 - 75 Exp - Average monsters give 1-2xp, it would take about 50 kills to level
Level 10 - 100 Exp - Monsters give 2-4xp, it would take 33 kills to level
Level 20 - 125 Exp - Monsters give 4-5xp, it would take 28 kills to level
This is backwards of what it should be, although you are fighting stronger things you also are getting stronger.
2: Fix the shop, it breaks your view now. Why not disable the custom view altogether? Being the source engine it is prone to bugs anyway.
4: The level up system is BORING at low levels (partially due to #1), this gamemode could really use an attribute system. One skill every 5 levels is meh. I'm sure this is already expected but here are some ideas anyway that aren't stupid.
Endurance - Increases your stamina recovery and health
Strength - Increases your stamina and damage with sword
Dexterity / Agility - Increase movement speed and damage (or accuracy) with weapons
Intelligence - Increase mana/rate
5: Remember to list a #3
6: Make it so when buying ammo you don't spend money on ammo that you can't carry, same for potions and everything else
7: Tailor the game towards lower levels, move the higher level spawns (like those screaming things to the right after leaving town) farther away. Or solve this by leveling faster early on - Farming headcrabs in the spawn area is BORING but outside you risk getting raped by Gonomes and "hot pockets" (baby headcrabs).