1. An 'add to new playlist' function
On the Android app it is possible to search for an album, then add it as a new playlist. For some reason on the iPhone app, you can't do this, meaning you have to find an album, then switch to Playlists, then create a new one, then switch back and add the album in. Not such a good user experience.
2. Scrolling track titles
Currently track titles (or indeed any displayed content) doesn't scroll. Not good when you're looking for the Evolution of Dub Volume 3 album and can't differentiate between that and the others in the series because they all display as "Evolution of Dub Vo…"!
3. Landscape view
Its something of an addendum to the comment above, but if the app could go into landscape mode, I could see longer track names. Or in other words: please bite the functionality of the iPhone's native player 
4. Better means to organise playlists
On all Spotify clients you currently cannot organise your offline content in any way. OK, so I believe on the desktop app you can drag them around to re-order them, but you cannot organise them alphabetically or indeed by any other means. With an ever-growing number of playlists (32 and counting) I'm currently in scrolling hell.
5. Means to add tracks from one playlist to another
Let's say I download a complete album. Then, I realise I only like 2 songs from that album and would rather add them to a "Songs I Like" playlist, meaning I could then delete the full album offline playlist to save space. Would be handy, no? But at present, it cannot be done. OK, hardly a deal breaker, but iPhones still only pack limited storage when you consider the old days of 80Gb iPods (that also didn't need to store apps, email etc etc) so hence its worth removing deadweight tracks if it saves some space, right? Damn right…
Let's be clear though, on the whole I am LOVING Spotify as a mobile experience. Unexpectedly it has become a valuable source of music discovery for me, with ever more obscure artists and labels being added by the day. Entire Wordsound back catalogue anyone? (And god knows, that was hard enough to find in physical form here in the UK!) Rare Basement 5 album, produced by Don Letts? Disco Dub Band? Sopwith Camel? Aynsley Dunbar? All there - and all eminently worth checking out I might add…
Of course you could do worse than check out the playlist from the Mr Trick & Wrongtom radio show too
