I have the Olive 4HD. Bought it last summer before the 3HD came out.
I like the 4HD. Setting aside the musical qualities, which are very nice, there are two essentials to getting maximum use/enjoyment out of it.
First, despite the fact that it has a touchscreen and remote, the best way to control the unit is through the iphone/ipod/ipad app. My weapon of choice is the ipad and it truly makes the Olive fun to use.
The second is the manner in which you import music. Until very recently I used the internal drive. This works fine except for the fact that Olive's source for meta-data - and specifically album artwork - blows. So I started ripping CDs on my PC (as FLAC files) using the dBpoweramp software and then I move them to the Olive via Ethernet.
The whole digital server market seems to be moving pretty quickly, which is a great thing for the consumer. Nine months in, I am not sure if the Olive is the best solution but it works well for me. Were I to do it again today I might go for the 3HD simply because of the lower price point in the event a needle-moving solution comes out in the next twelve months.
Like many people comment about these things - be they Olive products or otherwise - you do find yourself listening to a lot more music this way - which is a very good thing.