The first one is: make it possible for users to download Ovi Store without creating an Ovi account. Creating an account first is annoying, and you do not want to annoy people that quickly. Account creation can be delayed until the first purchase is going to be made.

Second suggestion: after installation, the Ovi store app has to be in the root folder, not in Installations. There will be lots of users that download Ovi Store as their first app, and they do not know that Installations is the first folder to look into when an app has been installed. They will think that installation has failed, which is bad because they will think that all installations wil fail.
AFAIK, it is possible to specify the target folder in an apps reg file in resource APP_REGISTRATION_INFO using the group_name field, this works for non-root folders, might work for root too.
Ideally Ovi Store would be in the position next to the default active app when a folder is shown, but AFAIK that is not specifyable in the reg file. It can however be the default position when Ovi store is in the firmware.

Third suggestion: do not show a users id in the main screen as it detracts from the important info, which are the apps that can be downloaded for free or for money. When the user starts a download, logging in is early enough. Ideally, the user will be logged in automatically, or after giving the password only, as the user name should be known to the Ovi store app.

Fourth suggestion: when Ovi store start up, it must not ask for a network connection all the time. It should be possible to set such a connection once, and have a Settings item to change it. Again, usres must not be distracted from the downloading experience.

Fifth suggestion: when selecting Applications, show the applications subcategories and not apps, or make it clear that this is a special selection.

Sixth suggestion: when moving from Applications to Games, make the search button show Search games immediately and not after the games catalog has been downloaded. This makes the program appear to be much more responsive.

Seventh suggestion: cache the visible parts of the catalogs and show these as soon as the user switches to a new main category. This also makes the program appear to be much more responsive. If necessary, only cache text, not images so there's more room.

Finally a defect report: there is a defect in Ovi Store in the main category selection: if you go from Applications to Games to Audio & Video, the system sometimes goes back to an earlier choice. So you have choosen Audio, which begins to download the catalog, and then you are dropped in Games again. This is on an E71 with the latest firmware.