I agree with the OP, the new store is a pain to navigate. I can't find the sale section anymore, so now if I want to see if the game I want is on sale I have to check them one by one. And what's with the search option? Instead of simply type in the game you're looking for, you have to choose a letter, and then it gives you a list of EVERYTHING with that letter in the title!
Overall I think the redesign is an improvement over the old store. As far as certain items missing and some features not being entirely 100% perfect I think it's important to maintain a set realistic expectations. This is a complete redesign from the ground up. Give Sony some time get get it perfect.
The other frustrations from not knowing how to do "x" will disappear as you learn the new layout and navigation. I bought some DLC for Mafia 2 last night and it was much easier to find and buy than in the old store. Search > Mafia 2 > scroll to where it says Add-on Content and presto.
Try doing that with the Soul Calibur 5 dlc. Not only will that not show up, but it won't even let you put the word Calibur in the search. Simply putting in Soul only gives you a link to the PSP SC game and nothing more. I went to the add on section to try and find it in the jumbled mess and nothing was there. Heck I never even spotted the SC 4 add ons anywhere. The old search function worked perfect and I never had these issues.
I just logged in and wanted to just head over and see if there was any new DLC for a single game. I had to DL the new store, then log in, then I see the store and it's all crap. The new store sucks. I mean really sucks. The user interface looks cool, but is terrible. You can't look at games under a single letter anymore, you have to scroll through them all in order to find a game you are looking for. The entire thing is nice looking but doesn't work for crap. I used to be able to go into the store (which would load instantly) and locate the games I own and find add-on and or updates and get them done in less than five minutes. NOW, I have to spend a half hour looking through everything to see if I have something or not, and then the store still shows my missing things that appear in game, or that my history shows I purchased. Not only that, but I'm almost positive that this update has somehow managed to cause me to loose DLC that I've purchased for games... again. I don't care how pretty something is as long as it works the way it should and this new update to the store doesn't work. It's inefficient and the user experience has just been clobbered. Fix it.