Right now I have to keep refreshing to get it to even load an asset.
Same issues inside and out of Unity, this seems to be a very common problem and has been going on for months now.
I am having the same problem …extremely slow asset store in-editor …I am unable to download any asset update or new purchases …keeps giving me an error about not being able to download the update or file…
same here, i must log out to search through asset store and then log in to purchase or add to wishlist etc. dosn’t work good and is very limited even if work 
Oh you know… They have probably used an old computer as the store server, one that was spare. Probably an old spectrum or vic20, Or judging by the number of times it seems to not be working, probably a zx81 with extender cartridge. Maybe they should put it in a room without a door!
THIS is what I am talking about …really frustrating …
…but the fact that my laptop works fine loading the Unity Asset Store in the editor with the same Unity 3D version as my desktop seems odd to me…
You have no idea, even inside unity, I have been trying to download my assets for close to 7 hours today, and I am not even 1/3 of the way through my assets, let alone my mixamo animations… it is ridiculous.
It’s been slow for a long time as far as I can remember.
Sometimes it’s insanely slow. They really need to do something about it.
I know right, it looks like it is going to take me over 50 hours just to download all of my assets fresh, due to a disk failure 
Browsing the Asset Store is impossible from my tablet or smartphone (Android 4.4 and Chrome) because it fails loading the website.
I could live with the slowness for now if the would only fix the download page so that it doesn’t reset to the top of the window and re-expand everything I have collapsed… its very frustrating. Anyone know of an alternative way to download your assets?
It stuck twice while downloading an asset and then the third just downloaded it fine. Maybe i connected to the right place the third time ?
I have a shortcut to the downloaded folder so I can just manually import assets. I used to use the store for that but it got too slow and didn’t even load most of the time. For browsing for new assets I use the web version of the store.
What sucks is having to update the assets, it takes forever just trying to log in, find it, download the update, deny the import, then go back to the asset store window and find that it probably failed somehow with the Kharma web bug or whatever and I have to reload Unity and pray it loads up so I can update another asset. Really needs to be optimized. The interface update earlier this year seems to have made it slower than before.
Everyone that thinks the asset store is slow should vote on this topic.
http://feedback.unity3d.com/suggestions/speed-up-the-asset-store-online-and-inside-unity3d