So, let me start by saying that I as a player saw some of the potential problems heading into the event, I think a lot of players did and we didn't voice those concerns ahead of time when they could have been fixed. So, players are at fault too.

I didn't personally voice mine because I didn't want to see a repeat of RTCF where prizes got severely shifted between tiers, that just got messy.

So my biggest issues with the event were...
-Vague language that leads to uncertainty - "don't worry about limits" "here's a rough guide but there may be surcharges" etc.
-Post purchase changes
-Tier loot mismatches

Vague language - I had more than a dozen conversations with people prior to the event that always ended with two catch phrases from me. "Don't trust those costs there are always surcharges." and "There are always limits."
We as players going to these events always want to be prepared. Nothing sucks more than winning a tier then not being able to afford to buy the service you won. It's an emotional rollercoaster that would likely cause some players to smash their heads on the wall. To offset headsmashing doctor bills we try and go in with the philosophy that overprepping is better than underprepping. So anytime you can give us a method of calculating exact costs for our specific cases, we're usually happier. I know some people are convinced surcharges were added after the fact, and who can say? However, I think the final chart that came out was awesome for all involved.

Post purchase changes - I think this is already done, but trying to limit these is important. Nuff said.

Tier loot mismatches - This is a big one. I think first and foremost tier and prizes should be discussed before the event's setup. I think there were some T1 items that didn't deserve T4 status as just a small sample. Tiering should always include the entire spectrum of uses/situations if possible.

Any generic repeatable upgrades to specific items should always be considered for all tiers and separated accordingly. By repeatable I mean anything that can applied to the same item over and over for increased benefits - weighting, padding, enchanting.
What I would have preferred to see for padding for example would have been...
T1 - up to WCP
T2 - up to FCP
T3 - up to MCP
T4 - up to HCP

Just an example, same would apply to weighting. Also, some formerly coveted upgrades just aren't that great in GS4. DB items and defender items do not hold the value they once did. Personally my DS fluctuates so much on any given attack I don't even notice my DB item. Permablessing is also lackluster now because it prevents other benefits from being applied. Rune tattoos shouldn't have been in the T1 tier unless they included non-standard scroll spells because they are simply self recharging scrolls.

So my advice, discuss prize quality before the event's underway.

That being said I think a lot of great things were done this event- Ticketing, Tiering, clear pricing, posted scheduling. I spent a lot less time worried I would miss something by sleeping this event than I did at RTCF.

Dgry