no issues with 9855 that i'm aware of if you buy the current australian versions. top HU.
the blau is more powerful in terms of tuning ability, and a more 'complete' tool for this purpose. very hard to beat. so if you want a HU 'with the lot', strongly consider the blau.
alpine's alternative is to add their outboard processor, the PXA-H701, which really gives serious tuning ability and some other features (like dolby digital 5.1 if you have a DVD player). but for $999 plus the remote control face $499, it comes out expensive.
still, the 9855 is no slouch with tuning ability, and beyond what most people would ever utilise to full potential.
so if you want a top quality HU with 'very good' tuning ability, the 9855 could be a goer. if you want the option to expand on this by adding the PXA processor, it's also worth considering (yet a cheaper option would be a $500 alpine HU + processor). if you want a HU with 'excellent' tuning ability, consider the bremen.
note that i've never used the bremen, and only speak of its reputation. but i have used alpine for years, including 7998/9835/7990(current) and processors PXA-H600/510/900(current).