I have the LinkedIn (Beta) and while it's not super functional it gives me updates, lets me add an updates, search, and see my contacts but that is the limit of what it does. It has a 3 star average but for a viewer only its decent to use.
If it gets more functionality like Droidin has I'll be happier.
THere is also linkedin mobile web which I haven't tried. Also there is DroidIin lite and Droidin. DroidiIn Lite is the trial/free version of Droidin. I haven't used it but the comments are iffy for lite and almost 4 for Droidin ($2.00).
I haven't tried either but if the beta I have doesn't improve I might.
Plus, so far there's really no revenue model to make anybody really interested in developing the "real" app.
Cheers,
Bo Stone - DroidIn creator