Not necessarily "old" tech, but the 899 or Legacy series I think they call them have been out for several years, and HB felt like it was time for a new product. HB will STILL support this series for several years to come, so. There is not much you can do to "improve" 2d sonor, just better screen quality to show a prettier picture. SI & DI can be improved with better transducers (HB has a HD version for more $$) but there is noticable improvement in what you see on the HU in the SI mode, but I'm not sure about the DI mode.
I plan on using the 899 in DI/2d mode more than anything else since the xducer will be on the TM up front, and the SI pictures on the HU get distorted due to directional changes in the TM. I also got this unit because it is compatible with the ILink unit which allows me to upgrade from the Ipilot I currently have whenever HB comes out with the next generation of Ilink. I'll buy then instead of the $800 price tag now. Lots of guys just have to have the latest and greatest gadget, I'm content to be a generation or two behind in fishing technology since I'm in old fart territory, and not willing to spend my $$ on the latest/greatest conversational piece of equipment. It does take a lot of time on the water to learn new electronics, which seems to take away from the actual fishing in some aspects so I'm not willing to spend the $$ and the time when something new comes out. LOL