I've had a C120 for 2 seasons. It's an excellent unit, and very easy to use. Mine's cockpit-mounted, under the sprayhood, and is visible in most lighting conditions. The MARPA feature is useful, but does need a fast compass input for best results. The radar/chart overlay is great, and I use it a lot. Go for the biggest screen size you can fit/afford (and remember the C120 has 800x600 pixel resolution - over 50% better than the C70/C80).
There are still some great deals going for the Raymarine RL70CRC which include radar. I've got one. They work out at less than the price of the C series plotter without radar.
We also have a C120 in the cockpit and fully agree with everything pvb has written.
So easy to use and now that navigation can be done in the cockpit, my good wife who suffers from seasickness at the chart table, is able to navigate as well. She calls it navigation for dummies!
This summer coming out of Arisaig in 500m visibility we had 6 targets to deal with as soon as we cleared the entrance. It was a busy 5 minutes until I had them assessed for risk but without MARPA it would have taken much longer. MARPA is great and has significantly reduced the stress of poor visibility for us.
They upgraded the C series last month to include AIS (data comes in via rs232 from a nasa engine or other) with decent looking CPA, TCPA etc stuff .. am also thinking of one of these .......
Have the C80 incl. fishfinder and radar.
Very satisfied, although radar resolution is limited.
Recently installed new SW version and downloaded Raytech Planner offering possibility for planning routes and/or storing waypoints on normal (home) PC and transfer data via CF card.